Reaver
Newcomer
Playing split screen on Switch, if player two goes into the volcano on Ginger Island the levels are all a repeat of the same map up to level 5, at which point a water river blocks further access. If both players are doing volcano and player two goes to the next level first they get the same base repeat level, of player one joins they see the normal next level, with a ghost of players twos map layered on top. If player two leaves the level then rejoins player one it works.
Happens multiple times, different switch hosts on different save files. Doesn't happen if playing local connection, just split screen.
Switch, version 1.6. English. No idea how to upload save files but since it's on multiple devices and different save files I don't think that's the root issue.