Puzzles bug

So on mobile, when you go to the next puzzle level, the board turns grey and it tells you what puzzle level your on. But not the whole board is grey: 

On the left

what is wrong here

There is a line

If I'm not mistaken, that's just the left boundary of the chessboard?

Yeah shouldn’t it be grey???

Well, if you look at the right side of the board, the gray stretches over it, so it might just be a positional bug in the app/web's code.

I'm confused nothing seems wrong