Wandering Traders will occasionally not take emeralds in trades.

You have to possess enough emeralds to fulfill the transaction 1 to 5 times. Beyond this amount of emeralds, Wandering Traders will not take emeralds and will give one free item before deactivating the trade. This appears to be from holding SHIFT while trading in order to auto-trade, as clicking through the trade one at a time avoids the issue entirely.

Expectation:

With trading villagers, such as farmers and blacksmiths, an excess of emeralds will not ruin the trade, and the trade will proceed up until it is deactivated. E.g. if a trade takes 5 emeralds to give 1 item, you can attempt to trade 5-64 emeralds.

What actually happens:

With Wandering Traders, the trade will only work if you possess enough emeralds to complete 1 to 5 transactions. E.g., if an item costs 4 emeralds, you can trade anywhere from 4 to 20 emeralds and the trade will proceed as expected. If you try using 21 emeralds, you will only receive one item, lose no emeralds, and the trade will be deactivated.

 

 

How to replicate:

1. Summon or locate a Wandering Trader.

2. Find a trade that you have more than 5x the emeralds for.

3. Attempt to trade. Hold SHIFT and click the trade item.