Mercedes Benz Umhlanga

I purchased a brand new Mercedes Benz C200 Coupe in August 2017. As Mercedes Benz Umhlanga ("MBU") were not prepared to order me a vehicle to my specification I ordered it from Malmesbury and took delivery at MBU, the dealer closest to me. In October 2018 the sunroof exploded whilst I was driving on the freeway. MBU indicated it was not caused by a manufacturer default despite articles indicating the issue of exploding sunroofs in other countries. My insurance covered the repair. In December 2018 I had a breakdown and was advised that a fuel injector needed to be replaced. This is an extract from an email to me when I queried what the issue was - "The failure on the injector is caused by the internal piezo on the injector, we have also found a factory safety recall campaign that is due on your vehicle to which my team have completed." On 23 January 2019 I had a breakdown again. Just a few weeks after the prior one. At that time I requested full diagnostic testing to establish any and all issues with the vehicle. I was again advised that it was fuel injector and requested an explanation as to why similar problems were being experienced again. This was the response received - "The repair carried out on your vehicle when it came in to us in December necessitated the replacement of injector number 4. We have carried out similar repairs to other models with similar injectors where the replacement of a single injector has remedied the problem. However there have been instances where further injectors have needed to be replaced to fully remedy the issue. Please understand that MBSA are the custodians of the Motor plan attached to the vehicle and authorisation to any repair lies solely with them. MBSA have since modified the repair process when it comes to faults of this kind pertaining to the injectors. Based on the result of certain tests that we need to carry out MBSA will now authorise the replacement of all 4 injectors. We are in the process of carrying out these tests on your vehicle. Once the tests are complete we will forward the information to MBSA and await their response which should be authorisation to replace all 4 injectors." I was thereafter informed that all four fuel injectors were replaced. I followed up on the full diagnostic report but nothing was forthcoming and this was the email that I then sent to MBU - ""Further to our previous correspondence, I just wanted to let you know that since I collected my car after the replacement of all the fuel injectors it has been running well. Regarding the full diagnostic test, Tracy confirmed that it was done and that no faults were identified. I was however not provided with anything in writing and just wanted to ensure that we had a record." On 12 February 2020 I again had a breakdown and my vehicle is still at MBU as at today, 20 February 2020. They have provided me with a loan car. I have since last Thursday been trying to get details as to what the exact fault is and there has been mention of fuel injectors as well as other parts being ordered however nothing is being committed to writing. My queries were around the lifespan of a fuel injector, if it needs to be replaced every 12 months, then why isn't it done as part of the service if it is a part that has such a short life span, are the parts being used not of inferior quality, etc. I would firstly not expect to experience problems with a new vehicle and secondly repeated problems related to the same part. To date my queries have been ignored and I have included several MBU staff members in the email but no feedback to the queries raised. MBU did advise today that all the parts are available and the vehicle is being repaired however they have still not advised as to what specifically is being repaired and I also want to know what caused the repeated breakdowns. I have indicated that until I receive a response to my satisfaction I will not be fetching my vehicle. It clearly appears as if they do not want to commit anything in writing as they don't want to incriminate themselves. I have also contacted Mercedes Benz South Africa today and have not as yet received any feedback. Any guidance as to how to proceed as well as feedback from others who may have experienced similar issues with the same model of vehicle or MBU would be welcomed.