This bug can be found across *ALL* voidrig necramechs. Ability 1 doesnt work, using it prevents any melee actions from happening for the remainder of the current mission. The bug happens due to using the first ability. There are no other pointers towards the cause, ability one by default doesnt work, do not use it. I first encountered this bug by occupying a rouge voidrig in cambion drift, I was hopefully assuming that it was exclusive to the case of it being a rouge rig, sadly no. Cool bug, forced to build bugged feature for story progression 😉
There is no fix, ending the current mission is the only way to undo the bug. Using ability 1 will immediately cause it to happen again.