Hi Laranz,
We kinda fixed this problem buy returning to each portfolio item, opening each single image we already added to the portfolio item and saving it again. it sounds ridiculous but it worked. It seems a small bug in your theme. If you can check it out it would be great..maybe other users found the same problem.
We now have a different problem we will pose to you in a different post, ok?
Thanks for answering.
Manifestoworks