This has been a bug forever and I’ve expressed its great annoyance in another thread too but please I’m getting so tired of being trapped on UW a floor for hours or basically until the floor resets because for some reason the stairs down have disappeared seconds after spawning and you can’t dig a hole because you lack the required digging skill or you are deeper than 150 or you just NEVER fall down a hole. Of course I fall down a hole every 5 minutes when I’m search for chests but when the hole is actually needed it never appears which is so very typical of the crappy RNG in this game.
I am on 146 and don’t have quite enough digging to go deeper but regardless I wouldn’t be able to dig any more if this happened deeper than 150 in any case which it has and probably will again.