diff --git a/app/src/services/sync.js b/app/src/services/sync.js
index 1477e3d2..47743d17 100644
--- a/app/src/services/sync.js
+++ b/app/src/services/sync.js
@@ -175,7 +175,39 @@ const service = {
 
         // Case: not in COMS - insert new COMS object
         else {
-          const objId = await service._deriveObjectId(s3Object, path, bucketId);
+          let objId = await service._deriveObjectId(s3Object, path, bucketId);
+          let existingComsId;
+          try {
+            existingComsId = await objectService.read(objId);
+          } catch {
+            // Derived object id not currently in use by COMS
+          }
+
+          // Object id in 'coms-id' S3 tag already in use in COMS:
+          //  Delete the 'coms-id' tag on the new object,
+          //  so that we don't attempt to re-use an existing COMS object id.
+          if (existingComsId) {
+            const sourceObject = await storageService.getObjectTagging({
+              filePath: path,
+              bucketId: bucketId
+            });
+
+            // Workaround for deleting just the 'coms-id' tag (S3 can only delete ALL tags on an object):
+            // Retrieve all tags, delete all tags on object, then re-add all tags except 'coms-id'.
+            const objectTags = sourceObject.TagSet.filter(
+              x => !sourceObject.TagSet.includes(x.Key) && x.Key != 'coms-id'
+            );
+            const data = {
+              bucketId,
+              filePath: path,
+              tags: objectTags
+            };
+            await storageService.putObjectTagging(data);
+
+            // _deriveObjectId() doesn't care if it conflicts with existing coms-id's,
+            // so generate a new one after deleting the S3 tag
+            objId = uuidv4();
+          }
 
           response = await objectService.create({
             id: objId,
diff --git a/app/tests/unit/services/sync.spec.js b/app/tests/unit/services/sync.spec.js
index c0d24a64..a1c64442 100644
--- a/app/tests/unit/services/sync.spec.js
+++ b/app/tests/unit/services/sync.spec.js
@@ -348,9 +348,11 @@ describe('syncObject', () => {
   const _deriveObjectIdSpy = jest.spyOn(service, '_deriveObjectId');
   const createSpy = jest.spyOn(objectService, 'create');
   const deleteSpy = jest.spyOn(objectService, 'delete');
+  const deleteObjectTaggingSpy = jest.spyOn(storageService, 'deleteObjectTagging');
   const getObjectPublicSpy = jest.spyOn(storageService, 'getObjectPublic');
   const pruneOrphanedMetadataSpy = jest.spyOn(metadataService, 'pruneOrphanedMetadata');
   const pruneOrphanedTagsSpy = jest.spyOn(tagService, 'pruneOrphanedTags');
+  const readSpy = jest.spyOn(objectService, 'read');
   const searchObjectsSpy = jest.spyOn(objectService, 'searchObjects');
   const updateSpy = jest.spyOn(objectService, 'update');
 
@@ -391,6 +393,10 @@ describe('syncObject', () => {
 
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(0);
+    expect(readSpy).toHaveBeenCalledTimes(0);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(0);
     expect(deleteSpy).toHaveBeenCalledTimes(0);
     expect(getObjectPublicSpy).toHaveBeenCalledTimes(1);
@@ -429,6 +435,10 @@ describe('syncObject', () => {
 
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(0);
+    expect(readSpy).toHaveBeenCalledTimes(0);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(0);
     expect(deleteSpy).toHaveBeenCalledTimes(0);
     expect(getObjectPublicSpy).toHaveBeenCalledTimes(1);
@@ -467,6 +477,10 @@ describe('syncObject', () => {
 
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(0);
+    expect(readSpy).toHaveBeenCalledTimes(0);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(0);
     expect(deleteSpy).toHaveBeenCalledTimes(0);
     expect(getObjectPublicSpy).toHaveBeenCalledTimes(1);
@@ -494,6 +508,7 @@ describe('syncObject', () => {
     headObjectSpy.mockResolvedValue({});
     searchObjectsSpy.mockResolvedValue({ total: 0, data: [] });
     getObjectPublicSpy.mockResolvedValue(true);
+    readSpy.mockImplementation(() => { throw new Error(); });
 
     const result = await service.syncObject(path, bucketId);
 
@@ -504,6 +519,10 @@ describe('syncObject', () => {
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledWith(expect.any(Object), path, bucketId);
+    expect(readSpy).toHaveBeenCalledTimes(1);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(1);
     expect(createSpy).toHaveBeenCalledWith(expect.objectContaining({
       id: validUuidv4,
@@ -538,6 +557,7 @@ describe('syncObject', () => {
     headObjectSpy.mockResolvedValue({});
     searchObjectsSpy.mockResolvedValue({ total: 0, data: [] });
     getObjectPublicSpy.mockImplementation(() => { throw new Error(); });
+    readSpy.mockImplementation(() => { throw new Error(); });
 
     const result = await service.syncObject(path, bucketId);
 
@@ -548,6 +568,10 @@ describe('syncObject', () => {
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledWith(expect.any(Object), path, bucketId);
+    expect(readSpy).toHaveBeenCalledTimes(1);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(1);
     expect(createSpy).toHaveBeenCalledWith(expect.objectContaining({
       id: validUuidv4,
@@ -575,6 +599,60 @@ describe('syncObject', () => {
     expect(objectModelTrx.commit).toHaveBeenCalledTimes(1);
   });
 
+  it('should insert new object when not in COMS when it has a conflicting coms-id S3 tag', async () => {
+    const comsObject = {};
+    _deriveObjectIdSpy.mockResolvedValue(validUuidv4);
+    createSpy.mockResolvedValue(comsObject);
+    headObjectSpy.mockResolvedValue({});
+    searchObjectsSpy.mockResolvedValue({ total: 0, data: [] });
+    getObjectPublicSpy.mockResolvedValue(true);
+    readSpy.mockResolvedValue(comsObject);
+    getObjectTaggingSpy.mockResolvedValue({
+      TagSet: [{}, { Key: 'coms-id', Value: validUuidv4 }]
+    });
+    deleteObjectTaggingSpy.mockImplementation(jest.fn());
+
+    const result = await service.syncObject(path, bucketId);
+
+    expect(result).toBeTruthy();
+    expect(result.modified).toBeTruthy();
+    expect(result.object).toEqual(comsObject);
+
+    expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
+    expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(1);
+    expect(_deriveObjectIdSpy).toHaveBeenCalledWith(expect.any(Object), path, bucketId);
+    expect(readSpy).toHaveBeenCalledTimes(1);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(1);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(1);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(1);
+    expect(createSpy).toHaveBeenCalledTimes(1);
+    expect(createSpy).toHaveBeenCalledWith(expect.objectContaining({
+      id: expect.stringMatching(uuidv4Regex),
+      name: path.match(/(?!.*\/)(.*)$/)[0],
+      path: path,
+      public: true,
+      bucketId: bucketId,
+      userId: expect.any(String),
+    }), expect.any(Object));
+    expect(createSpy.mock.calls[0]['id']).not.toEqual(validUuidv4);
+    expect(deleteSpy).toHaveBeenCalledTimes(0);
+    expect(getObjectPublicSpy).toHaveBeenCalledTimes(1);
+    expect(getObjectPublicSpy).toHaveBeenCalledWith(expect.objectContaining({
+      filePath: path, bucketId: bucketId
+    }));
+    expect(headObjectSpy).toHaveBeenCalledTimes(1);
+    expect(headObjectSpy).toHaveBeenCalledWith(expect.objectContaining({
+      filePath: path, bucketId: bucketId
+    }));
+    expect(pruneOrphanedMetadataSpy).toHaveBeenCalledTimes(0);
+    expect(pruneOrphanedTagsSpy).toHaveBeenCalledTimes(0);
+    expect(searchObjectsSpy).toHaveBeenCalledTimes(1);
+    expect(searchObjectsSpy).toHaveBeenCalledWith(expect.objectContaining({
+      path: path, bucketId: bucketId
+    }), expect.any(Object));
+    expect(objectModelTrx.commit).toHaveBeenCalledTimes(1);
+  });
+
   it('should drop COMS object when not in S3', async () => {
     const comsObject = { id: validUuidv4 };
     deleteSpy.mockResolvedValue(comsObject);
@@ -591,6 +669,10 @@ describe('syncObject', () => {
 
     expect(ObjectModel.startTransaction).toHaveBeenCalledTimes(1);
     expect(_deriveObjectIdSpy).toHaveBeenCalledTimes(0);
+    expect(readSpy).toHaveBeenCalledTimes(0);
+    expect(getObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(deleteObjectTaggingSpy).toHaveBeenCalledTimes(0);
+    expect(putObjectTaggingSpy).toHaveBeenCalledTimes(0);
     expect(createSpy).toHaveBeenCalledTimes(0);
     expect(deleteSpy).toHaveBeenCalledTimes(1);
     expect(deleteSpy).toHaveBeenCalledWith(validUuidv4, expect.any(Object));