I hit this issue with almost 100% when I had a bunch of autominers I forgot about (without anything to process the chunks) in one location.This terrain issue is most likely a race condition during generation, timing or edge case related, which makes it non-deterministic and so infrequent and hard to track. Tiles aren't reused in the same way other objects are, because terrain needs to be created from scratch every time.
We're focussing heavily on fixing bugs at the moment, so hopefully a lot of these issues will be fixed soon.
Tell me more.
The sheer number of resource chunks caused a good amount of lag (which I believe is a known issue), but more interestingly it caused this terrain issue pretty regularly in the nearby biome seams.
Haven't encountered it at all since cleaning up all the resource chunks from that area.. but that might be a way to repro.