So through my testing, having the Ronin Rho mech (in the controller) will make Rob Repairo unusable for any vehicles, and both the Rho mech and Sigma mech will be unrepairable if in the controller (they show up, along with all other vehicles, but are at 0 health and no auto chips will be accepted for them.)

If you have a mech deployed you can fix them that way 100% of the time (as long as you don't have a filled Ronin mech controller), but that's more pricy and not the way it should work.

Although very unlikely, this may be a conflict with another mod I may have, so if someone else can confirm, please do so.

EDIT: I bought another Rho mech and it works fine with that one now, for whatever reason. I don't know the causes of this bug any more then.

EDIT2: After further testing I have resolved that it may be the items themselves acting wonky, rather than the specific mechs. I did have them deployed on my ship just before finding this bug, so that may be part of it.