08-12-2020, 08:24 AM
Hard to tell because we only see the result. We don't know what you started with. The GIF is optimized, did you optimize it explicitly or did you start with an optimized GIF? These are easy to recognize: successive frames are usually smaller than the whole image and are in (combine) mode. In an un-optimized GIF, frames are image-sized and all in (replace) mode. If you started with an optimized GIF, then the successive frames don't totally overlay the existing frame and this could create the dissolution effect.
The solution: use Filters>Animation>Unoptimize on your source image before you do anything to it. This create a new, unoptimized image on which you can work. Re-optimize (Filters>Animation>Optimize (for GIF)) only at the end of your editing.
The solution: use Filters>Animation>Unoptimize on your source image before you do anything to it. This create a new, unoptimized image on which you can work. Re-optimize (Filters>Animation>Optimize (for GIF)) only at the end of your editing.