Environment:

• Minecraft 1.14 Pre-Release 2
• Vanilla, remote private server
• Java 1.8.0_51 64 bit local client

Steps to replicate:

1. Insert trade desire into trade window for multiple trades
2. Shift+click to trade all or continue manually trading multiple times
3. Villager no longer wants what you're trading or plays the "willing to breed" animation
4. Try to pull item back out of offer
5. Item is destroyed (not dropped or returned to your inventory)

Replication rate: seems pretty high, I haven't been able to completely isolate when it happens, seems more frequent with Master level villagers.