I am having the same problem on the 1.19 release.
It can, but in a different way. There are now no longer any lag spikes. I have been testing the issue - first in 1.14 so I could remember how to recreate it, then in 1.16 release candidate 1 to check if it was still happening. The result was mixed, with some times working as it should, and other times the issue persisted just like the previous 1.14 bug. I found out this had to do with the gamemode you were in when you pulled the entity through for a second time. Pushing the entity through a portal without an exit portal linked, loading the nether and coming back to the overworld can be done in creative mode. If you then try to push the entity through for a second time with the exit portal now generated, it has to be done in survival mode for the entity to go through. However if you are in creative mode, the entity will not go through the portal, replicating the 1.14 bug, but without the lag spikes.
This has happened to me as well, also on a world that was generated in 1.8. What I did was reset the end chunks and then there were no more issues. Check out this helpful tutorial here: https://www.youtube.com/watch?v=fGlqDBcgmIc
I'm having the same issue, I'm using 1.20.1 vanilla minecraft, and have killed at least 30 Elder Guardians without receiving a single armour trim. I've tried using non-looting too, as I saw a second bug report which claimed to get the piece after switching from a looting 3 sword.