This was fixed today, the land team was apparently in a bit of delay so they didn't get to it sooner.

It is indeed accidental, the result of a bug that produces such terrain artifacts since January 2023. The extent of the terrain misalignment varies greatly between small "inverted potholes" (spotlike bumps) and alarmingly tall and thick walls. The following aspects are common in all of them:

1: They always appear on a region border

2: They always appear right after rolling restarts

3: If you walk or jump on top of them, the simulator will be confused as to where your avatar should be positioned and it will start to bounce similarly to on top of banlines

4: They tend to appear again at certain spots while they never appear at others

The following aspects only apply to some of them:

1: Roadside land was reset to default when it was set for auction

2: Terrain was rebaked

3: Location is right on or very close to region corner

4: Terrain is very steep at region border

(These only applied to less than half of those I have observed. I have seen more than 20 of them in total.)

Without seeing how the simulators deal with terrain position on region borders I can only guess, but my suspicion from the beginning is that the two simulators get mismatching terrain position values after a restart and in combination with some or all of the other aspects I have observed, it results in this abrupt change of terrain height.

While roadside parcel auction preparations do seem to increase the risk of such terrain artifacts, at most of the locations there was no roadside terraforming in advance. The two factors that seem to increase the risk of these artifacts the most are steep terrain and region corners.

Unfortunately there is apparently no way to actively reproduce this bug, however copying the ground properties of some frequently affected mainland regions to test regions and restarting the test regions often (several times a day) should eventually bring out the artifacts.