Villagers on a vanilla multiplayer server will lose their profession level (Apprentice, Journeyman, Expert or Master) and reset back to Novice. These are villagers from a natural village using a combination of the naturally spawned Jobsite blocks and manually placed ones (such as the Brewing stand).

Not my server so I cannot gather more info than what the F3 screen can provide.

I don't play singleplayer.

Only reporting this here since no other bug-report mentioned 1.16.1 but this seems to be an issue as old as villager trading itself; reported as fixed several times (but here we are again).