Trembling

[Robi]

Add either a trembling (visual/audible) effect while mining blank cave walls or give some sort of brief warning "The cave wall trembles as you swing your axe". Specifically for cave-in tiles. Don't disrupt mining, just give a small clue.

Finding metal as a hermit really sucks sometimes. Probing cave walls can set a hermit back an entire 24hrs while trying to find some tin. The big boys will find it anyways regardless.
I feel like the visual/audible is a better option as it (I think) would negate any bots to some degree. Plus it requires you to pay attention.

If you were a neanderthal man wearing thorn bushes as clothes and you swung your stone axe at a wall and the earth above you trembled, you probably wouldn't swing it again.

[Robi]

Not to be confused with the Rumbling..