Villager doesn't refresh all of his trades, he refreshes some and some doesn't.
Villager has access to his workstation.
How to recreate this bug:
1. Unlock his trades
2. Buy/sell one trades (so it is locked) (in my case I sold pumpkins)
3. Wait untill that traider works at his workstation (dont close his GUI, you will hear a sound of his workstation )
4. When he refreshes his trades buy/sell one or more diferent trades (in my case I sold melons and bought golden carrots)
5. Close GUI and wait to refresh one more times
6. You'll see that he did refres trades but only those trades that you bought/sold before he refreshed his trades fir the first time (in my case pumpkins).

As you can see on the picture I sold pumpkins before he refreshed his trades, then I sold watermelons and bought golden carrots, and no matter how long I wait, i won't be able to sell watermelons or buy golden carrots until next minecraft day.

This bug is in every version since village and pillage update.