As far as I can tell, the logout and posting error issues are independent.
The logout issue is just because the forum software now logs you out of all sessions when you log out of one session. This is easy to reproduce just by using two browsers on your computer. Since TripleA always includes a logout as the last step, you always get logged out of your browser when posting, regardless of whether the post succeeds or not.
The posting error is something else, and since it doesn’t happen every time it is probably somehow related to server load. Unfortunately it seems to be working right now when I try posting with the debugger active in TripleA, I’ll give it another try when I see issues posting a real game.
By the way, the forum seems to have an attachment size limit of 1 mb now and not 1.5 mb, so the text under the attachment button isn’t accurate.