ID:1913993
 
Not a bug
BYOND Version:508
Operating System:Windows 7 Home Premium 64-bit
Web Browser:Chrome 46.0.2471.2
Applies to:Dream Maker
Status: Not a bug

This is not a bug. It may be an incorrect use of syntax or a limitation in the software. For further discussion on the matter, please consult the BYOND forums.
I'm using the latest byond version and this happens every time I edit a sprite. https://i.gyazo.com/51a1752c389b954511a4aa8782520a49.gif
This usually happens when you have a lot of icon states in an icon file. I had a similar issue like that before. My guess is that it needs to re-read/write the file each time the icon state has been edited (possibly sending the edited icon data to the file from the buffer).

edit: I like your Windows 98 compression for the gif, lol. 256 colors?
The list control has some performance issues with large numbers of icon states. There's already an issue for this so I'm just going to close this one.
Lummox JR resolved issue (Not a bug)