Skeleton glitches through (enclosed) blocks/walls

Skeletons CAN pass through a passage way where there is a trapdoor at the height of the 2nd block height, where zombies and any other mobs CAN NOT.

Also a built in skeleton, just seems to teleport out of a enclosed area.
It was made from solid stone blocks, but one side had one wallblock.
It seems that they might not glitch through full solid blocks though.

But since they are rubberbanding, and strafing like maniacs, and walking through areas no other mobs can, i think this is all related.
And its actually quite frustrating.