Not sure if this is the right place for this, but I've noticed mending is misbehaving now. Rather than mending being prioritised, XP is now being split between the item you're holding and your XP bar.
You posted it in the wrong place. I have moved it here. This is from the wiki. Maybe this is what you are experiencing.
It has always been a mojang thing. (Or has been for the most time that way) if you are wearing an item with mending but its full durability, it still counts as as being repaired, but since its full, its sent to xp bar my understanding for best practice since mending was introduced is that you shouldn’t be wearing gear with mending to maximize speed. Just hold it in your main hand/off hand and go one by one. (If you want to prioritize a single item)
I'll put it on the back of my backlog to eventually look at. Can't say it is a high priority. But I'll look at it
For the longest time now, in my experience, it's been armour, then sword (or whatever you used to kill the mob) then whatever's in your offhand. What I'm finding as of today is that the sword will always fully repair, but the item in the offhand will often not repair, or only repair slightly, even when not wearing armour.
Actually I think this might be it. EMC's XP clumping makes it so that all the XP dropped by a wither is bundled into one orb, which will then repair a single item
