Can confirm for an existing multiplayer world. Recreating the portal does not fix the problem.
However, I tried to reproduce it in singleplayer with a new world and there everything seemed to work as intended.
Edit: Newly created worlds are affected, too. See Daniel Melby's comment
Turns out, this was related to 61586. So, the issue is solved now.
as reported in MC-89952 (and I can confirm this for my multiplayer world), End portals are affected, too.