Switch Volcano crashes and glitches across levels (local co-op)

[r8zen]

Stardew Valley 1.6.9 build 37, split-screen local co-op.

Since the last update, we see two problems that make it impossible to proceed (in particular, getting 10 dragon teeth to build a Island Obelisk):

• When any of the players moves to the next level in the volcano, the game may crash. It seems more likely to happen between level 3 to 4 and 4 to 5. We couldn't find any dragon teeth in the previous levels. Maybe it crashes because the next level(s) would contain one?
• Like others have reported already, the second player may see a different level than the main one. Interestingly enough, one can see the other character in their own level on lava, rocks, enemies etc. As a workaround, the second player may exit from the same door and re-enter; this seems to always fix the issue.

We were committed into getting the Island Obelisk, so the crash bug is kinda wearing out our motivation to keep playing this game.