Symptom: You unZip your module file and re-zip it for some reason. Thereafter one or more image files are missing. You can’t find the missing images in any previously unzipped file but you do find images with the same name, differing only in case… e.g. myfile.jpg instead or MyFile.jpg.
Cause: Your unZip programme is only restoring one of the image files wherever a set of files shares the same name, differing only in upper/lower case. Effectively masking the image(s) that you want to recover.
Solution: Always use a unique name for images, case insensitive. Also, maybe the UnZip programme can be told to recover files regardless of case.
Workaround: Remove the masking images from the module. If necessary, use Tools…Remove Unused Images. Next time you UnZip, you should find the images that were missing from the zip file.