When saving an image with XCF compression enabled, closing GIMP, under some circumstances "Save" once more will NOT save with compression
When saving an image with XCF compression enabled, closing/reopening the image over multiple days and just working with it will eventually NOT save with compression. Sadly, I haven't figured out how to reproduce it exactly - but all the images where I enable it via "Save as", it eventually disappears (which I notice by file size having exploded, and then I do an explicit "Save as" once more instead of just a "Save" and there it is, an unchecked compression check box even though I never touched it again).
Edited by Ghost User