Transparency Bug

[savaonepunch]

Im trying to create gifs into jimp images then back into gifs. It works fine on some gifs but on some i get this weird bug: https://imgur.com/a/IlRYSLG

This is how I'm doing it:

GifUtil.read(file).then(inputGif => {
    inputGif.frames.forEach((frame, i) => {
        // create a Jimp containing a clone of the frame bitmap
        jimpCopied = GifUtil.copyAsJimp(Jimp, frame);

        Promise.all([jimpCopied, maskP]).then(function(images) {
            var lenna = images[0];
            //var mask = images[1];

            //lenna
            //.greyscale()
            //.mask(mask, 0, 0);
            const fCopied = new GifFrame(new BitmapImage(lenna.bitmap))
            frames.push(fCopied);
            GifUtil.write("my-creation.gif", frames, {
                loops: 0
            }).then(gif => {
                console.log("written");
            });

        });

    })

})

Sorry if its some limitation i missed.

[savaonepunch]

Sorry, duplicate report because i thought my first one didn't go through.

[EDIT]: Reopened because my first issue didn't actually go through.

[hisRoyalty]

same here, having same issues as above