running a lot of command blocks in a flat land with a 4 tick repeater clock
after about an hour of playing/coding the world "lags" causing mobs to stop moving and commands/clocks to pause.
This will go on for a good 20-40 seconds followed by a 2 second PULSE of it all working fine followed by lag again.
Placing blocks and player movement is fine. However sound gets lagged until world catches up.

Current fix: Completely close minecraft. Launcher as well (sometimes forced in task manager) and restart.

Not sure if the pastebin helps. All i could find of saved crash reports.
http://pastebin.com/Pc8SZ60M