Set Weapons of Same Type Won't Equip

Just curious as to if there is a way I can find out why certain set weapons, omni beam weapon in particular that are from totally different sets are unusable together. I mean they are different sets, have different procs and yet they still can't be used together. Put in a support ticket asking why this was and was referred to the forum as tech support has no answer to provide. Primary weapon is from Morphogenic Armaments set and there are several other set omni beam weapons that will not work with it, a standard omni weapon from outside a set will not work with it but most of the of similar set weapons won't equip.