Hey there, although already reported, there has not been any responses on the Critical Error "Assertion failed" I could find with a quick search. The Error happens to me only, if I have Dropbox running in the background and when I try to play rPVE. Usually I turn in off before playing BattleForge, but I sometimes forget which is a pain for other players, because when I load the Map, my game crashes and they are one player short. I assume it is kind of a read/write error of a file that is being synced by dropbox (I sync my whole Documents Folder with dropbox). I already tried to go selective sync on Dropbox, but it somehow always recreated the folder with a "conflict detected" tag (which I assume is a dropbox issue). Maybe you guys figure out a way to fix this, would be awesome :-)
If not - sorry to all the people who's game I left right after the loading screen, it was not on purpose