Thanks all for your replies and suggestions. Unfortunately things have got worse, with benches also now disappearing, along with their entire contents and placed thralls, plus other random items - transporatory stones, placeables, more thralls, etc.

I also suspected some sort of issue saving the game at some point that has ended up corrupting it. And as I don’t have a recent save to fall back on (my fault) - I don’t think there’s much I can do except call it quits on this run through and start again from scratch.

Thanks again for your replies / suggestions - much appreciated!

Cheers