I don’t know if this is new to 2.5, but I just noticed something weird.
If you paste background images into a glyph (say from Photoshop), Glyphs creates a .tif file in a folder called “Images” next to the .glyphs file. If you paste an image into, say, an uppercase E, Regular weight, it will create a file called E-Regular.tif in /Images. However, if you then paste an image into the lowercase e, it will attempt to create a file called e-Regular.tif. Unfortunately, the OS is case-insensitive, so the older file, E-Regular.tif, gets overwritten and the lowercase e image will subsequently appear in the background of the E.
As far as I can tell, the only work-around is to create the image files ahead of time and drag or import them into Glyphs, rather than using the paste feature. It’d be nice if this could be changed so it doesn’t overwrite existing images that have been pasted in. It’s much quicker and less tedious to use copy and paste than to create a bunch of files manually. (Typically, when I need to do this, I have all the character scans in a single image file.)
(I know it’s technically possible to change the OS to be case-sensitive, but I’ve heard this can cause problems since this is not the standard system setting.)