Put the summary of the bug you're having here
What I expected to happen was...:
Enchantments of first and second item (diamond sword) should add together
What actually happened was...:
Enchantments of second item were ignored. Tried multiple swords.
Steps to Reproduce:
1. Put sword in first slot
2. Put sword in second slot
3. Anvil did not have red X, so should function
4. Put cursor on result sword, no new enchantment from second item
Same issue