I've had the message pop up that my sword is disabled at 1 durability, but my sword breaks. happened 5 times in a row now.

Using project mmo, so that might be messing with it

I decided to disallow interactions for two reasons. First, so that the mod can be a client-side tool that works in vanilla servers, and second, so that the repair mechanics of mods would still work. If I had make it a special broken item, that would have worked for vanilla items repaired in the anvil, but then mod items and modded ways to repair wouldn't have accepted the items as replacements for the original.

That said, I do not know why it would fail, it should be cancelling the interaction, both the left click and the right click...

Just had it work with a axe while chopping a tree. I'm surprised you didn't go with making it a broken item. That might be why it's failing at times.

could be because low skill=more durability use in project mmo. I've never had an issue with mod repair mechanics using the ruined equipment mod in fabric. Is there a way to just tell minecraft that if durability is less that 1, to make it 1?

Would love to hear back from you on this, if you've got time.