Steps to reproduce:

1) Find yourself a trial chamber where mobs spawn intensively.

2) Grab a bow with Mending enchantment and stacks of arrows.

3) Attack the mobs constantly with the bow.

4) Analyze the behavior of the bow while attacking mobs and absorbing experience orbs.

Expected result:

The enchanted bow should remain fully charged without being influenced when experience orbs are absorbed. In this period, you must keep the right key of your mouse pressed.

Actually:

The bow recharges after the absorption of orbs and you should charge it again. Otherwise the bow will only shoot very weak arrows.