Crewdroog: gog got back to me, and I'm not very happy with the reply:
Hello,
Please try clearing your browser's cache, performing a clean refresh (Ctrl+R) of the page, and then logging out, and back in.
If you're using intrusive plugins, like JavaScript and ad blockers, please try disabling these, to see if they were causing the problem
If this doesn't help,
please try using a different browser altogether and let me know if that helped.
That last bit made me quite annoyed and it looks like he/she didn't even notice that i'm not the only one with this problem.
That seems to be their standard answer whenever something is not working correctly. That is why I now always directly tell them that I already did all that stuff, since these are always the first things I check.
I had the crash problem again today... and that even with only the chat open and no other tab -.-