Searched, and didn't find this, so creating.  It may explain some of the "Missing bees in villages" reports:

I watched a bee get "walked on" by a villager when it was flying low to the ground, a grass path block, and it flashed red and then died.

I'm not sure if it's something to do with the grass blocks being less than a full block high, or some interaction with the villager, or both.