Okay, I tried your proposal, it was definetly not the fast travel mod, disabled and uninstalled it, still crashed within minutes.
After I disabled all mods, is worked. Now I have to go through the progress of testing every single mod untill I find the one that causes this, while I have no clue which could even trigger EXP gain in any way. Since this will take some while, so will my next report, but I will report back, so if this happens again, you are familiar with a likely suspect
EDIT: Did it all now, tried all mods one after the other, no success, game didn't crash again. But there is one mod that gives EXP, "JCDEnderalWorkersApartment" which is also the reason I lost 70% of all my equipment because I stored it in containers provided by the mod when I forgot they weren't standard... it's all gone now. So I don't know if I will continue to play, what turns all this effort to dust, especially since I couldn't find out the culprit.
Again thanks for you effort