Performance Issue

Usually my framerate is about 40fps however in this snapshot it's constantly below 15fps. My framerate seems to be unaffected by my video settings.

My measurements:

20w22a ( performance is the same with 2 chunks and 12 chunks ) :

fps 13-15

minimum frametime 5-70ms

average 70ms

maximum frametime 70-900ms 

20w21a ( 12 chunks view distance) :

40 fps , minimum frametime 10-20

average 25ms

maximum frametime 30-60ms

20w21a ( 2 chunks view distance) :

80-110 fps

minimum frametime 4-10ms

average 10ms

maximum frametime 30-60ms