In my office my CAD file has some xref's, for easily working and drawing I need to unload and reload them. But after some time some xref's stop reloading. I am the only one with this problem in my office but also the only one with AutoCad LT for MAC, and some xref just unload and reload when I want, but some files don't and the only solution seems to be to delete/detach and attach it again. Visretain is 1, links are properly attached and names didn't change.  What can be the bug here?