Gah! Misread your post, sorry BraveSirRobin.
I did have issues with combat not triggering even when my characters weren’t stealthed, but only when they were either a way from the fight or at a different elevation from the enemies. I put this down to stealth weirdness, as there seemed to be stealth checks at least sometimes when my characters tried to attack even though they weren’t actually stealthed.
But this issue does sound different and worse.