For non-hacker clbum characters I’m pretty sure the negative stats happens when the server barfs as you send it the equip or unequip message. It unequips instead of equips or unequips twice. At least, that’s my theory behind it. I don’t think it relates to anything other than a bad communication to the server.

I haven’t played with hacker stats at all so they might have a bug if they lose stats more frequently.