Captain reported refusing the aircraft for a ferry flight after Maintenance couldn't sign off or MEL a door rigging problem without additional inspection and repair.

Narrative

This was to be our one leg flight from ZZZ to ZZZ1. As we arrived at the gate we were informed by the Gate Agents there was a mechanical on the aircraft. We subsequently found out that the inbound crew wrote up the cockpit overhead light illuminating indicating the R2 door was not secure. The flight attendants also corroborated the report indicating that the door handle on the inside of the cabin was physically raising upward approximately 2 to 3 inches. The flight attendants also indicated that when they attempted to lower the handle to its normal secure position; it would not remain in place and kept raising up again. No other details or indications were noted in the logbook. In our subsequent conversation with the Maintenance Personnel; after he went back and looked at the door; he said 'this was bad' and after further review he indicated would not sign off the aircraft for further revenue service until it received proper maintenance and inspection. That was that. After the fight was officially cancelled; the flight crew remained with the aircraft until it was determined what would be the next step. We contacted crew scheduling; as did the flight attendants for further instructions. We subsequently heard back that we were to ferry the flight back to ZZZ1. My FO (First Officer) and I were a little uneasy about this and I wanted further discussion with Maintenance and Flight Operations. My subsequent discussion with Maintenance did not allay our concerns very well as I expected; at the very least; a more robust system would be put in place to secure the door. My FO (and her husband who was traveling with us) are both engineers who both worked and are currently working for Company and provided valuable insight and ideas about door testing and safety. They were not satisfied that ferrying the aircraft in its current state would be considered safe. Also taking into consideration that the Maintenance guy indicated he would not even sign this aircraft off for a ferry flight. We subsequently had a discussion with Flight Operations who also included one of our Check Flight Pilots in our group discussion and after tossing ideas and suggestions; I decided not to take the aircraft back to ZZZ1 in its current state. I was extremely fortunate to have the expertise of my FO who happened to have worked as an engineer at Company who had significant amount of knowledge on door testing and operation. Her husband who traveled with her is also a current engineer at Company and was able to add his valuable input. I realize we can't always have experts travel with us on every flight depending on the issues that may arise; but it once again shows how important it is to be able to gather as much solid information as possible before coming to an important operational decision. The Maintenance guy also made the decision pretty easy as well.