It is impossible to use redstone or the chat(commands included)

The only  the current chunck stays loaded

The world cant be saved(if attemted it just shows the page "saving world" but nothing happens; new client locks world since it is still in use)

The instance can't be closed(even with task manager, I had to log off)

The Player can't fall out of the world

Movement is still posible

Blocks can still be placed and destroyed

I hope the info helps with fixing the problem. Thanks in advance.

Ps.: I let MC run in the descibed coditon without closing it and it started to work again after  ~15 min.