I don't understand when Mitsubishi don't come to the party, WHY put it in and pay them to carry out the necessary repairs ????
and then need to return because of dodgey work needing rectification
Their test drive would involve driving around the block, trying to talk to the techo who performed the work would be like asking a jeweller can you just duck out to the car to show your grandmother the new watch you intend to buy her, no way in hell is it going to happen,
I,m pretty sure there would be gearbox specialist who are fully aware of the gearbox issue by now and can offer the same service if not more thorough, at a discounted dollar figure, and stand by their work unconditionally and will fully explain whats causing the issue, and how the repairs will rectify the problem from reoccurring.