Watch this video so that you can understand what was happening: 

Video

Steps to reproduce: 

0. Run a bedrock server(localhost preferred but you MUST run a server, instead of using the internal one in the game), and move into the end demension with a legal end protal.

1. Make some ender men mad, then go inside the end portal with them following, which should transfer you back to the normal world. (Before I recorded the video above, the enderman appeared to be blocked by the bedrock along the end portal)
2. An invisible enderman should be attacking you when you transfer back. 

Probably because the server considered the enderman was already transfered, but client didn't "know"? 

P.S. Not tested on local world yet. This might not happen on LAN games.