Mysterious freeze in a certain area

Recently, I noticed a HUGE frame drop in a certain area of my world (not only in one chunk), the game even freezes completely and the FPS fluctuates between 1 and my normal 60 FPS..
One thing is for sure, it isn't caused by a surplus of entities, as it seems to happen in an area where the entity count is only around 100 (after switching to pieceful to get rid of egg holding zombies who may be causing this).

I forced a crash with F3+C and attached the report. I hope this can be resolved..