Structures and natural decorations get smeared in converted 1.17 worlds

I converted a world created on 1.17.11 (seed: -6643344; all experimental options on at generation except "additional modding capabilities" and "Holiday creator features"; survival mode, normal difficulty) to 1.17.30.25. last week.

Today, after exploring some distance from my base, I entered a village of the taiga biome type.  About 4 houses were cut in half and part-submerged in a lake.

Other abnormalities such as a free-standing submerged ladder and a campfire burning underwater were also present in/near the transected buildings. 

Screenshots attached.

Similar to reports MCPE‐45096 and MCPE-45870, but these are extremely old and not in reference to 1.17.