For anyone struggling with the auto button:
Seems the button function for pause and auto is shifted half of their size to the right from the actual display.

Also it was mentioned just earlier, it should be possible to get a copy of both 5* tanks by the end of the event as F2P. That would require work everyday though, but it is definitely possible. I feel the event is fair, but obviously a little more expensive to get the extras. That said if you've been saving up on cores, 1000 cores for guaranteed 5 star is pretty good deal.