Playing on a Realm.

I cannot reproduce, it happens randomly, but a lot today.

4-5 times.  Locked-in and name tagged librarians have changed their trades.  I name them by what important books they have, that is how I know the trades were lost.  I also have all the books documented.

It is a largish number of villagers, enough that 3 iron golems patrol.  They are free roaming with their workstations in certain areas per job type.  I am only really working with the librarians right now, trying to get all the books.  But I have others that I use to get more emeralds.

My process is:
isolate them
to break/place the lectern until a desirable trade is created
trade paper a few times to lock in
name tag them and document the trade
if really valuable or the trade I really want is further down, perhaps get to the apprentice level
let them roam free.

I am playing on a realm (achievements), but not mine, so my hands are tied in testing, can't get a backup to show/prove.  I am methodical and detail oriented.. so programmer to programmer, I assure you, I did not accidently not lock them in.

Thank you.