Gary - photo of damage, showing the bottom face. The light stuff is some blue-tack that got stuck in the crack. As far as I can see, the crack does not go all the way through the bullet wall. (PS I don't have short thumbs - its a perspective thing).
I tried it today and got no readings at all. Tried blue-tacking it in several locations in the bilge, but only occasionally got a faint smudge on the display when I pushed it down really hard with my hand, and no numbers on the display. I'll check for a loose connection with the head later (thank you, hindsight), but if that does not work, the unit is a dud.