Clipping through blocks

So i was going to make a mini game where zombies attack villagers and you have to defend them (Unoriginal, I know).I figured it wound be easier to use a suffocating kill system to kill the zombies when each time it tried suffocating a zombie it vanished. I then started to test why this was happening so that I could fix it. After some testing I realized that each time a zombie was being suffocated it could clip though anything. After that I went to the bug report to report the issue and found out that someone was crushed by gravel and clipped through everything until he reached the void. Then I realized that any entity that was effected by gravity would fall to the void if crushed and that this would break any mob farm that uses a crush system (which is pretty much all of them).