Since the latest update i am regularly encountering this bug. Clicking on the arrow that usually takes u back to the main mtt-lobby (marked in red on image) has no effect after all.
It usually happens after playing for a couple of hours. In the beginning it mostly works fine, but sometimes also requires mashing the arrow 3-4 times before it actually works. Before the update I never had this kinda problem. Sucks for an MTT-player because I often can't keep regging MTTs ingame. Only thing that seems to be working is closing the client and starting it again (which is obviously not a solution at all).