I got a villager that I traded with and renamed it Mao Mao the Channeller. As obvious as it is, it trades Channeling book. If you look closely, it has the brown badge already as proof that it has levelled up from trade.
But then Mao Mao is not trading Channeling book but now is selling bookshelf and a Respiration book in its second tier trade.
The experience bar is also resetted to zero EXP with “Apprentice” Title on the top part of its trade window. But then again, brown badge on the outfit and an unlocked second tier trade even when resetted to zero exp.
We're tracking this issue at MCPE-117852, so I will resolve and link this report as a duplicate.
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