Thanks. I know what a check and checkmate is
I might be a terrible chess player but this I know. What I'm talking about are what very much seem like bugs in the game to me.
I'll give you an example from an actual game:
I open with pawn to e4, then black moves d5. I capture at d5 and black moves knight to f6. I revert to before the knight move to move the queen instead but gets the message "can't put the king in check". This is absurd as there is nothing to check the king at this point.