Friend unable to hit mobs but I can

I had to make this ticket a second time because it got closed for "Duplicate" even though I couldn't find a single fix for this issue with only one person on the server so I'm just making it again.

My friend is unable to hit any mob on the server. They're still hurt by hostiles, but can't hit back. We both have the same mods installed, with the correct Forge version. My game runs just fine, it's just that theirs isn't. They're opped, with PVP and animals on. I don't know why it's only happening with them.

Forge version 1.19.3 (44.1.5)

Mods installed:

JourneyMap, Easy Villagers

No, I deleted their file and they still aren't able to attack anything. Also, this may be useless but I noticed that, when they try to attack something, their arm doesn't even move like they're trying to hit it at all.

Is there any way I can tell you that without having it posted on a public ticket? I would rather not have random people joining my server and knowing my friends' username

I emailed [email protected], thank you