This is an update to an issue I had reported and was rejected on a few weeks ago, as I have found more info. I was making a skyblock map when my game had performance issues a lot while building in the nether. Striders were the only mobs spawning, and upon setting up a repeating command block to kill them, the game started running smoothly again. I believe this has something to do with striders spawning at the bottom of the lava and slowly floating to their proper spot. If any further info is needed, please let me know.