We've noticed some serious clipping as well on VON on our server.
Dedicated server and we can get it to happen with as few as 20ish. Explosions and a good amount of activity (players and AI) seem to have some adverse effect. though when we cleaned it up (dead AI) there was still a significant issue.
Noticed it recently as well, but was not paying attention so I can't say it's tied to 1.18.