Where are these ground paths?
anything that has an electrical link that reaches the coax sheild
TV's, a person's hand touching the case of a reciver, anything that makes contact with the ground of a reciver (HDMI cables, other connection cables
its fully possible that the splitter is dieing but saving everything else
a code violation is a code violation and having another home's ground in your home and still thinking of them as ground is just going to lead to something bad
do it right or expect problems, and the right way is a ground block at one of the (or both) homes and bonding the ground rods