These issues are similar but unrelated. The resolution steps suggested also do not work. This is biome dependant as well, meaning when I leave the Ancient City it works just fine.
Issue is still active. Mineshaft spawned above and the mobs are spawning on blocks below the Mineshaft as well.
Hi - The main issue doesn't link to MCPE-98789, The chief complaint in there was "void" and these are all Overworld issues. The overworld is unaffected in this - it only affected the nether and filled it with Netherack - not VOID. Furthermore, this issue still persists. Please take a look into this - the issues are most DEFINITELY unrelated to overworld generation, but nether generation.
I can reproduce this by throwing an Ender Pearl to the middle right of a nether portal frame properly while in the nether. Inversely, Throughing pearls in this way at an overworld portal divides your coords by 8 teleports you there in the overworld. Video to come.
1.20 full release have detached tops example on new world