Well then I can not say what your issue is then.
The script is not designed for integrations to be switched. Now the script I linked which is this. Reassign userid's when switching integrations to VBulletin
It basically checks the photos comments and resets the userid based on the vbulletin username. This would have to have been the first thing you do after you reset photopost to use vbulletin.
Now if you did like a username resync in Scan database which does the opposite and resets the username based on userid which of course would not match because of the phpbb to vbulletin import I can see this happening.
If for some reason the username is not correct on those photos there is nothing the script I wrote can do for you. Basically your only way of correcting the issue now would be to assign those photos to the proper user by editing them as admin and assigning them to the proper user.