Cannot move / glitchy movement

Something has happened to my main world. After exiting the previous day properly and returning the following day, when entering the world, I can barely move. I can look with the mouse but the movement keys (WASD) barely respond and the screen jitters. After moving a few pixels, it just stops and all I can do is look around with mouse, interact with objects (furnaces, chests, etc nearby) and click escape - so not a keyboard issue. The other worlds I have saved can be accessed with no issues.

Looks like something has caused corruption but the world still looks ok?

I have crashed minecraft (using f3 + c) and attached.

This is rather annoying as the last back-up of my main world was over a 3-weeks ago and when popper into save folder works - so it is something with the current save?

I'd appreciate if you have a solution as I would hate to have to roll back 3-weeks.