I have been trying to make guardian farms work again. This time, there is a change I cant get around. Guardians that fall off a ledge of water at the end of a chute, drop a few blocks then fly/hover. If you log out and log back in, they fall properly from their hover position. Attacking them causes them to bounce up a few blocks then they drop back down to their hover position. 

It appears if they jump off a ledge, or are pushed off they fall properly, but if they fall off they hover.