New Challenger problems

We bought the new PB Challenger and took delivery in mid Jan. The car ran fine for the first 5000km. I had a set of electric brakes installed the last week in Feb. Drove the car home, noticed a funny noise when parking in the garage but wasn't sure if it was the car or the roller door coming down - so I turned the car back on and it started fine. Went to go out later that evening and the car wouldn't start. It would turn over but wouldn't ignite. NRMA came out but couldn't diagnose the problem. Five week old car loaded on the tow truck and carted to the service department. Turns out the computer was shot, service manager wouldn't commit to it being a electric brake problem, but that was more likely than it being a vehicle fault he said. After five working days in the shop I got the car back but it wasn't performing the same as the first five weeks. You would be cruising along the highway and it would shudder every now and then, pulled in to get petrol and it wouldn't lock, started running rough on cold start, stability control wouldn't kick in. After driving it for three days like that we took it down a dirt track to try out the 4wd, after getting back on the bitumen the car was like back to its original self. It was already booked in to be looked at so took it in, but of course nothing showed up and the suggestion of putting it in 4wd had helped was disregarded. After running it for a week we took it back to the dealership to discuss hooking the electric brakes back up, the auto electrician was keen to get together with the service manager to check out the wiring diagrams, but the service manager didn't want to. In the end it was organised through the dealer principle that their auto electrician - who is a mate of ours - would check his work, turned out all was good there so brakes were hooked back up and no problems. Looking like a vehicle fault. The car is still shuddering when cruising at a steady speed, like it is trying to decide what gear it wants to select, but service have no fix and the best they could offer was to get us to note down when it has a problem to see if there is a pattern - like I have nothing else to do - emailed the dealer principle today with a weeks worth of findings and just got the brush off.
I am now very disappointed with the car and the after sales service - or lack there of. Would be interested to hear of anyone else who has one or a Triton with similar problems, Cheers Michelle