Game window freezes completly but world is still running

Sometimes when playing a a particular survival world I created in 20w45a (and am now playing in 20w46a) the game will completely freeze but doesn't stop running.

I can tell this because the sound still plays. I can continue to do things like walk and open my inventory(shown by my mouse appearing/disappearing) and I even managed to save and quit to title (didn't help, still showed the same desert village house. If I press the ESC key the appropriate saving chunks for levels appears in the logs, and my mouse reappears but nothing else unusual is happening in the logs.

I am unable to be able to regularly repeat this, but is has happened 3 times in about 3-4 hours of play.

Edit: Formatted, spelling and still happens when I bump allocated Ram from 2 to 4 GB