If you stack up, like, 15-20 sand blocks and cause them to fall, it will cause a lot of lag, compared to in previous 1.17 snapshots. Seems to happen on and off.

When this occurred, I was draining an ocean monument. If I restarted my game the issue would be fixed for about 30 minutes before the issue would come back on and off. My normal fps while recording is 30-60 fps but as you can see in the video it dropped to about 1 fps for a while