diff --git a/Changes b/Changes
index 3057c43ca..b09ee866a 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,12 @@
 CHANGES LOG
 -----------
 
+0.27.0
+ - check for divide by 0 when calc samtools subsample value
+ - drop file check, explictly assume fastq.gz files are gzipped when calc #reads for salmon
+ - make the code flow more robust in cases of insufficient reads for salmon
+ - unconditionally remove auxtags before adapter clipping when realignment_switch is 1
+
 0.26.0
  - add parameters file for top-up merge
  - functional equivalence: enable selection of markdup method - biobambam (default), samtools or picard
diff --git a/data/vtlib/pre_alignment.json b/data/vtlib/pre_alignment.json
index 61cfc1405..dd6d970d6 100644
--- a/data/vtlib/pre_alignment.json
+++ b/data/vtlib/pre_alignment.json
@@ -25,13 +25,12 @@
 		"type":"EXEC",
 		"use_STDIN": true,
 		"use_STDOUT": true,
-		"cmd":[
-			"bamreset",
-			{"subst":"resetaux_flag","required":"no","ifnull":{"subst_constructor":{"vals":[ "resetaux", {"subst":"resetaux_val", "required":"no", "ifnull":"0"} ],"postproc":{"op":"concat","pad":"="}}}},
-			{"subst":"auxfilter_flag","required":"no"},
-			"level=0",
-			"verbose=0"
-		],
+		"cmd":{"select":"realignment_switch", "select_range":[1], "default":0, "comment":"remove aux tags unconditionally for realignment (realignment is non-default)",
+			"cases":[
+				["bamreset", "resetaux=0", {"subst":"auxfilter_flag","required":"no", "comment":"auxfilter=comma separated list of aux tags to be kept if resetaux=0"}, "level=0", "verbose=0"],
+				["bamreset", "level=0", "verbose=0"]
+			]
+		},
 		"comment":"Alignment removal also required for bamadapterclip (at least 0.0.142)"
 	},
 	{
diff --git a/data/vtlib/salmon_alignment.json b/data/vtlib/salmon_alignment.json
index 968784fa9..61db99e0e 100644
--- a/data/vtlib/salmon_alignment.json
+++ b/data/vtlib/salmon_alignment.json
@@ -99,16 +99,16 @@
 					"--geneMap", {"subst":"annotation_val", "required":"yes"},
 					"--output", {"subst":"salmon_out"},
 					{"subst":"b2c_mt", "ifnull":{"subst_constructor":{ "vals":[ "-p", {"subst":"b2c_mt_val"} ]}}}, "\";",
-					"case `file $0` in *ASCII*) PART1=`head -n 1000 $0 | wc -l`;; *compressed*) PART1=`gunzip -c $0 | head -n 1000 | wc -l`;; *empty*) PART1=0;; esac;",
+					"PART1=`gunzip -c $0 | head -n 1000 | wc -l`;",
 					"if [[ $0 && ! $1 ]]; then",
 						"SALMON_CMD+=\"-r $0\";",
 						"if [[ $PART1 -lt 1000 ]]; then",
-							">&2 printf \"Not enough reads to run Salmon: fq: %s\" \"$((PART1/4))\"; exit 0; fi;",
+							">&2 printf \"Not enough reads to run Salmon: fq: %s\\n\" \"$((PART1/4))\"; echo 'NO_ARCHIVE_SE'; exit 0; fi;",
 					"elif [[ $0 && $1 ]]; then",
 						"SALMON_CMD+=\"-1 $0 -2 $1\";",
-						"case `file $1` in *ASCII*) PART2=`head -n 1000 $1 | wc -l`;; *compressed*) PART2=`gunzip -c $1 | head -n 1000 | wc -l`;; *empty*) PART2=0;; esac;",
+						"PART2=`gunzip -c $1 | head -n 1000 | wc -l`;",
 						"if [[ $PART1 -lt 1000 || $PART2 -lt 1000 ]]; then",
-							">&2 printf \"Not enough reads to run Salmon: fq1: %s - fq2: %s\" \"$((PART1/4))\" \"$((PART2/4))\"; exit 0; fi; fi;",
+							">&2 printf \"Not enough reads to run Salmon: fq1: %s - fq2: %s\\n\" \"$((PART1/4))\" \"$((PART2/4))\"; echo 'NO_ARCHIVE_PE'; exit 0; fi; fi;",
 					"$SALMON_CMD'",
 					{
 						"select":"alignment_reads_layout",
@@ -118,38 +118,42 @@
 							"1":[{"port":"fq1", "direction":"in"}],
 							"2":[{"port":"fq1", "direction":"in"}, {"port":"fq2", "direction":"in"}]
 						}
-					}
+					},
+					"&& echo 'DO_ARCHIVE';"
 		],
 		"comment":"salmon is too fussy and requires a minimum of good reads to work or it throws a fit. wrapped in a bash script to validate fastq files"
 	},
 	{
 		"id":"zip_salmon_quant",
 		"type":"EXEC",
+		"subtype":"STRINGIFY",
 		"use_STDIN": true,
 		"use_STDOUT": false,
-		"cmd":[ "zip", "-r", {"subst":"zip_target"}, {"subst":"quant"}, {"subst":"quant_genes"}, {"subst":"lib_format_counts"}, {"subst":"libparams"}, {"subst":"cmd_info"} ]
+		"cmd":[
+			"bash -c 'ms=`cat`; if [ \"${ms}\" == \"DO_ARCHIVE\" ]; then >&2 printf \"Found archive instruction, so zipping\\n\"; zip -r $0 $1 $2 $3 $4 $5; else >&2 printf \"No such file, so no zip: %s\\n\" $1; exit 0; fi'", {"subst":"zip_target"}, {"subst":"quant"}, {"subst":"quant_genes"}, {"subst":"lib_format_counts"}, {"subst":"libparams"}, {"subst":"cmd_info"}
+		]
 	},
 	{
-		"id":"quant_genes",
+		"id":"archive_decision",
 		"type":"RAFILE",
-		"subtype":"DUMMY",
-		"name":{"subst":"quant_genes"}
+		"stubtype":"DUMMY",
+		"name":{"subst":"archive_decision", "ifnull":"archive_decision.txt"}
 	},
 	{
 		"id":"cp_quant_genes",
 		"type":"EXEC",
 		"subtype":"STRINGIFY",
-		"use_STDIN": false,
+		"use_STDIN": true,
 		"use_STDOUT": false,
-		"cmd":[ "bash -c 'if [ -e $0 ]; then cp $0 $1; else >&2 printf \"No such file: %s\" $0; exit 0; fi'", 
-				{"port":"src_quant_genes", "direction":"in"}, {"subst":"quant_genes_target"}
+		"cmd":[ "bash -c 'ms=`cat`; if [[ \"${ms}\" == \"DO_ARCHIVE\"  ]] && [[ -e $0 ]]; then >&2 cp -v $0 $1; else >&2 printf \"No quant_genes file: %s\\n\" $0; exit 0; fi'", 
+				{"subst":"quant_genes"}, {"subst":"quant_genes_target"}
 		],
-		"comment":"if salmon is not run this file is not created"
+		"comment":"if salmon is not run the quant_genes file is not created"
 	}
 ],
 "edges":[
-	{ "id":"zip_salmon_output", "from":"quant_genes", "to":"zip_salmon_quant"},
-	{ "id":"salmon_to_quant_genes", "from":"salmon", "to":"quant_genes" },
-	{ "id":"cp_quant_genes", "from":"quant_genes", "to":"cp_quant_genes:src_quant_genes" }
+	{ "id":"salmon_to_quant_genes", "from":"salmon", "to":"archive_decision" },
+	{ "id":"zip_salmon_output", "from":"archive_decision", "to":"zip_salmon_quant"},
+	{ "id":"cp_quant_genes", "from":"archive_decision", "to":"cp_quant_genes" }
 ]
 }
diff --git a/data/vtlib/subsample.json b/data/vtlib/subsample.json
index a537d1f88..271cf6ca2 100644
--- a/data/vtlib/subsample.json
+++ b/data/vtlib/subsample.json
@@ -42,7 +42,7 @@
 		"use_STDOUT": true,
 		"cmd":[
 			"bash -c '",
-			{"subst_constructor":{"vals":["tmfs=\"", {"subst":"tag_metrics_files", "required":true}, "\""],"postproc":{"op":"concat","pad":""}}}, "; if [ ! -z \"${tmfs}\" ]; then for tag_metrics_file in ${tmfs}; do reads_count=`jq", {"subst":"jqkey", "ifnull":{"subst_constructor":{"vals":["'\"'\"'.reads_count.\"", {"subst":"s2_tag_index", "required":true}, "\"'\"'\"'"],"postproc":{"op":"concat","pad":""}}}}, "${tag_metrics_file}`; reads_count=`echo ${reads_count} | tr -cd [:digit:]`; reads_count_total=$((${reads_count_total}+${reads_count})); done; frac=`echo \"10000/${reads_count_total}\" | bc -l`; fi;",
+			{"subst_constructor":{"vals":["tmfs=\"", {"subst":"tag_metrics_files", "required":true}, "\""],"postproc":{"op":"concat","pad":""}}}, "; if [ ! -z \"${tmfs}\" ]; then for tag_metrics_file in ${tmfs}; do reads_count=`jq", {"subst":"jqkey", "ifnull":{"subst_constructor":{"vals":["'\"'\"'.reads_count.\"", {"subst":"s2_tag_index", "required":true}, "\"'\"'\"'"],"postproc":{"op":"concat","pad":""}}}}, "${tag_metrics_file}`; reads_count=`echo ${reads_count} | tr -cd [:digit:]`; reads_count_total=$((${reads_count_total}+${reads_count})); done; if [[ $reads_count_total -eq 0 ]]; then reads_count_total=1; fi; frac=`echo \"10000/${reads_count_total}\" | bc -l`; fi;",
 			"if [ ! -z $frac ]; then",
 				"samtools",
 				"view",