Same with 21w05b and most likely any snapshot other than the latest. It's pretty much game over if you have a world there with some of 1.17 features - you can't open these in the latest snapshots with increased Y range.
Same with 21w05b and most likely any snapshot other than the latest
Why don't you just upgrade it to 21w05b? At first glance it resolves the problem.
I used all snapshots since 20w46a and for 2,5 months of server's uptime and probably hundreds of hours played such dismal failures never happened.
I may have some copper weathering near the place this crash happened if that has some connection to copper. We were in the Nether for some 10 minutes earlier with 2 players to check out if the water magically produced from glow litchen and lava stays there (it does 🙂 ) and it was fine. The crash happened later in the overworld (that's clear from the reports anyway).
I think in 1.17.10 with experimental features the sub-zero Y part actually does fall down, as I mentioned in MCPE-137755 (just the part above Y=0 stays levitating) so my bug is not a 100% duplicate, but whatever. My scaffolding did not start at Y=-64 though - there's normally bedrock there - it was from around Y=-58 up to Y=64. When broken at the bottom some of it fell down - I think up to around Y=0, the rest stayed on.