I did the Tiny Tina Mission where you get to re-kill the Last Bosses. And where they get “unbeatable” or something added as a title. After I killed them I killed the “Normal” Endbosses (Without paying Moonstone) 4 times in row. In the 5th time, while the big one was in his corrosive form, I started to move backwards without pressing “s”. “a” and “d” didnt work, “w” would stop me from moving. Opening the inventory would fix this for a minute, but then It’d start all over again. Also while pressing “w” to stay still I could not use any other keys to open the Inventory or pick loot up.
OSX on Steam with Athena.
Update : restarting the game helped. Didn’t try the Bossfight again so far