Q: 2016 Ford Flex making a clicking noise

We were in an accident. The rear passenger side tire was hit and damaged. They stated the suspenision need to be fully repaird, and switched out the tire and hub cab. After the repairs the rear end of our vehicle makes this loud clicking noise. Another mechanic found a loose bolt and tightened it. That same day we heard the clicking still everytime we would pull in somewhere or stop. The other issue that we are having is at times. It makes this grinding noise when reversing. It is not often at all, but it has happened more then once and nothing is rubbing against at the time. The two mechanics have stated the clicking is the exhaust cooling down, but the sound was not there before the accident and therefore we are concern, plus this grinding noise never happened before. Can you please give me some idea of what it could be.

My car has 6000 miles.
My car has an automatic transmission.