Sometimes that happens to me, but usually it is just my really bad internet connection. If you have a bad or on and off connection maybe it is that. If not i can't help i'm sorry
Resolved: "sticky cursor"

Moved this to the Help & Support forum, where you will hopefully get more help with your issue.
Also, are you using Chrome as your browser by any chance? It seems like a few people have reported this bug with Chrome and for them it was caused by some browser extension. Not sure about it, though.

Which browser are you using?
Have you tried using a different one?
There are known issues with Chrome extensions ...
does-anybody-have-problems-with-chesscom-by-using-google-chrome
Hello there,
I am experiencing some difficulty making a move (any move) in my current game. When I attempt a move, the selected piece will mot leave the cursor, until I move the cursoe off the board, then the piece follows it !