Client renders chunks at wrong places, repeating the same chunk in space. Logging out and logging in helps. Other relevant glitches include invisible ghost blocks behind the chunk border and also invisible players if they're standing in affected chunk. The bug can be reproduced just by wandering around, it will show up eventually.

This bug may be related to MC-87007 and also MC-86996 as all of them happened in the same gaming session. I don't have enough information to judge, just pointing that out.

Haven't noticed this bug with previous snapshots, so it may be related to recent optimizations.

Visible cuts in the islands on the first screenshot are on the chunk borders. The second one is taken from the same place after re-logging. The world save itself seems to be unaffected and world generation looks just fine.