I built an Enderman farm in the End and the Endermen appear to be teleporting to things and places that they did not in the past. I used the same design and all surfaces are either made of glass, chests, Enchanting Tables, Endstone brick bottom slabs/stairs, carpet, buttons or glass with Redstone and Redstone repeaters.

In 1.15.2 I didn't run into this issue whatsoever but now in 1.16.1 I am. In 1.15.2 If the rules Endermen fallow for teleporting changed, I didn't see it written down or talked about anywhere. Also if it matters, I am on a Realm.

You can reproduce this by going into a void world, making 2 platforms, 1 glass and 1 any material. Spawn the Enderman on the NOT glass platform then cover it with water. You will see some of the Endermen teleport to the glass platform even though it's a transparent block.