So I was playing survival on the new snapshot, with the latest version of the caves preview datapack, when after a few hours of playing on the world I suddenly got a huge lag spike, and a couple blocks I had just broken reverted. After the lag spike, everytime I moved between chunks there would be a slightly smaller lag spike(half a second-a second). It would be temporarily fixed by leaving the world and returning, although it would happen again within a few minutes. I checked the F3 menu and something called "Scheduled Executables" was taking up more and more memory every time I moved between chunks before slowing decreasing back down to zero.

Update: it does not seem to happen in the nether. The game freezes upon leaving the nether.