I’ve noticed recently that about 30% of the times I open a game, it renders the board as very small and in the top left of the screen as shown in the screenshot below. When the page first opens, the board actually usually looks like this before going full size, but occasionally it gets stuck like this. I’ve also noticed that the rank graph in the profile page does this sometimes as well, also shown below (as I’m a new user I’m only allowed one photo per post, I’ll try to post the other one in a follow-up comment).
I believe this is (related to) a long standing bug, it happens sometimes for me as well. The board seems to resize once I click one of the arrows to move me through the game tree.