That would be a bug in vbgallery then in my opinion or at the very least a SEVERE limitation in that specific software. Remember on import we are simply moving the data to Photopost. Inputting photos and files are two separate actions. We fill our photos table with their photo info and then on the file import try and import the filenames that have been imported into our photos table.
See in Photopost we do not allow images with the same name EVER so on upload we change filenames. This is to prevent mix ups as you are seeing if you move an image to another category that has an image with the same name it would be possible to overwrite some other image. Therefore this is why on our upload we do our $imgchk routine on upload or edit of a photo.
Honestly I dont know offhand how to overcome that limitation in vbgallery since the import does not use the upload portion of our program which corrects imagenames. I bet this issue affects any image in the members gallery because images are in one category.
If I get some time I will look and see if there is anything I can do to overcome that vbgallery bug.