Tick lag insanely high right next to my base, but not outside chunk loading distance

[Greetings my guys]

Ok so, at -264 115 the game is a smooth 80 fps (which is insane because this works better than vanilla for me). At -265, 116 the game drops to 0 fps and the tick lag on the pie chart is 75%. One second I was in my base at 60 fps, then I just lagged out of existence. It took me about an hour to get out (I managed to fly away as a bat) but I don't want to start the game again, hate to say it. Why is the tick rate so bad after it was fine before, and I hadn't made any changes, and how do I fix it? theres no error logs, I dont think.

never mind, I went out of range, built a wall around the chunk borders, and somehow it started working at 115 fps on an 8 gig ram laptop. How, I have no idea. But im not complaining.