I've got a weird glitch

Hello,
I am writing to report a glitch that appears only when exporting my finished short animation.
The colors in the exported file are continuously flickering or flashing while that is not the case when I let the animation play on aesprite.
Your help is appreciated.

It sounds like you might be running into the limitations of the GIF format.

GIFs only support 256 colours per frame. If your animation contains more colours than that, the colours will be automatically reduced, and they may be reduced differently across different frames, causing flickering. You can prevent this by manually reducing the colour count while keeping colours consistent across frames.

Alternatively, export the frames as PNG images, and put them together into a video animation in a video editor, or into an APNG (animated PNG, which doesn’t have GIF’s colour limitations, but is not widely supported). If you need an animated GIF though, you’ll need to optimize the frames by hand. Some programs do a better job with colour reduction than Aseprite does, but no algorithm is perfect. Only you, the artist, can decide which colours are most important to keep.