Update: It just happened again. I launched a pawn two squares forward, it glitched, and it only allowed the pawn to move one step forward.
In Console, I have two potentially relevant errors:
Failed to load resource: /callback/user-vs-personality/save-crown
Uncaught RuntimeError: null function or function signature mismatch in wasm://wasm/00f51546
I'm experiencing way more than normal lagging wherein "mouse slipping" is happening.
Sometimes I move a piece, such as a bishop, along a diagonal but it will register a mouse click (that hasn't happened) prematurely. I then see an illuminated square, the screen freezes for a bit, and then I see the next move happen sans animation.
In other words, if the next move is the enemy Queen sliding down a file, I won't see that animation -- I will just see the board change after a strange pause.
I noticed a few others revived an old thread and reported something similar was happening.
I'm on a fairly powerful Windows 11 workstation running Chrome 119.0.6045.160, and an RTX 4070 with the Nvidia studio driver version 546.01.
It's not something happening system-wide, or in combination with any other screen events on my system. It's likely not due to hardware sucking up CPU resources suddenly.
Anyway, reporting this in case other users are experiencing something similar.