I created a world to play on LAN. World was created in 1.14.1 and upgraded to 1.14.2. When downloading and running the world on a 1.14.3 server.jar, no one is able to trade with any villagers who were past the novice level when the server was running 1.14.2. The trade screen momentarily flashes on and off for these villagers. Villagers at the novice level can be traded with normally.

Server is hosted on Linux using vanilla rules and server.properties options. World can be uploaded on request if needed (approx 64 MB).