[2.0.21] Stuck "1 entity is missing the material" only for one player

[mlomb]

Context
We are two players playing in multiplayer using the in-game "Host" option (no headless server). I am the host (mlomb).

Problem
There is a rogue "missing materials" alert that only appears to my friend (not the host). It should not be there, since there is nothing there. It does not clear on its own and it does not blink like all other alerts. It does not appear in the list of alerts either.

My POV (host, no notification):

mypov.png (952.98 KiB) Viewed 318 times

My friend's POV (client, shows notification):

friendpov.png (501.68 KiB) Viewed 318 times

friendpov2.png (103.29 KiB) Viewed 318 times

We both tried restarting the save and the game. The notification is still present for my friend but not for me.

I asked another friend to join the game, and he can't see the notification. It is somehow tied to plantita.

[Loewchen]

I will assume that you pinned the alert.

[mlomb]

You are right, we did not know (pinned by mistake).
I assumed that it would go away automatically. Why it should not?

Edit: to be clear, the alert is gone now. Thanks