Error "Unknown tag:" is logged

Can confirm 🙂

@@unknown, do you know how to reproduce it? Or when did the error appear for you?

Hello! The errors were logged after running the the commands up to the /setblock stone_button, and then hit the escape key. However, trying to reproduce this again does not yield the same results. So unfortunately, I can't provide reproduction steps either. 😞

Was there a zombie village nearby? This sounds like you both encountered MC-202186 by unknowingly following steps 3 - 6 of this comment.

@@unknown, I did not notice the errors right away but based on the other logged messages I assumed it had happened while reproducing MC-123696. However, the reproduction steps for MC-123696 use a the_void superflat world so there should not have been any zombie villages.
But thanks for pointing out that the same error message appeared for MC-202186. I will mark the reports as related.

I found a seed that generates a zombie village for the superflat settings in MC-123696. (I found the seed via this reddit post which uses an older version and different superflat settings, but I confirmed that it works in 20w51a with the superflat settings from MC-123696.)
Superflat Preset

minecraft:sandstone;minecraft:the_void;

Seed

63486455778136911

Coordinates

/execute in minecraft:overworld run tp @s 61.37 1.00 -118.53 -878.55 -6.45

Furthermore, the village is so close to spawn that the errors are logged immediately upon joining the world (for the first time) instead of waiting until the player pauses the game.

Thanks, it looks like that is MC-194132; I have added the preset, seed and coordinates there (I hope that is alright for you).
That would explain this error message (which I have seen now again).

Since the reproduction steps here were not known anyways, I will resolve this report as duplicate of MC-194132 and MC-202186.