I have found two hand crossbows, they are the only 2 I've seen thus far so I'm not sure if there are more. In any case my first was picked up and immediately equipped. No issues, could freely switch between my 2 melee weapons or any number of other weapons. As soon as I picked up the second crossbow and equipped both at the same time, any time I would try to swap weapon sets, or unequip the main hand weapon, the game would crash. I can unequip the off hand just fine, no issue. I've tried swapping the crossbow for the other (crash), dropping it (crash) and anything else in between. I have to use both or just 1 crossbow, the cursed crossbow. At least make it +3!