Mending doesn't always consume experience

Steps to Reproduce:

1. Obtain a damaged item
2. Enchant the item with Mending
3. Summon some experience orbs far from the player
4. Switch to Survival mode
5. Move towards the experience orbs while holding the Mending item

Observed Results:
The experience sometimes goes to the experience bar and sometimes to the item.

Expected Results:
The experience should only go to the item until it is fully repaired.

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Original Description:
Well I am using either my skeleton or my enderman farm for levels the levels are going mainly into my level bar and not my tools or armor first