sh20000sh

Seems like this is breach attempt from old exploit. When older version, you might observed log that says something like <known player> disconnected from <not matching IP address>.

Seems like this is some kind of side effect of patching that exploit (or just updating java version). I experienced server crash when server processing these kind of errors.

I support the op's suggestion. Non-seed items are keep stacking and not consuming.

Can confirm in all 1.20.2 snapshots until 23w35a.

This issue can be reproduced in vanilla minecraft. Actual condition for it is when fully built conduit damages hostile mobs, its particle shows during attack. It is expected to be those particle removed after those mob are defeated, but they still remaining. Version of following screenshot is 23w35a.

Considering its first reported version, it seems like related with 'flattening'. Decay related tag prior to this was 'decayable' and after then, it changed into 'persistent'. And tags in structure looks like hadn't touched.

I believe this is leftover from days when they had oak fences and nether brick fences only. They should have add nether brick fence gate and remove all connection with wooden fences IMO.

Present on 1.20.1

I saw an another room that mushrooms are present in 1.20.1 besides already mentioned case. And I tried to generate it with structure block, and it had mushrooms. It dropped as item immediately tho - this might be brightness issue I think.