Hello.
You can read the documentation on Sprite Packer here:
https://docs.unity3d.com/Manual/SpritePacker.html
But if you want to fix this issue, what I currently do is delete the AtlasCache/ folder after each build...
It's located in your project folder, next to Assets/ and Library/
Yes I know, not the best ideal solution, but it does the trick...
~ Yohan