I thought this might be useful to other Kadjar owners if they are facing similar problems.
My 2016 Reg Kadjar was going well for the first 3 years, that is until manufacturer's warranty. After that period, it slowly started displaying multitude of faults and warnings on the dashboard such as Check Injection, Check antipollution system and so on, in spite of being serviced regularly.
Things didn't change much even after taking it to the dealer who charged £99 inspection fee.
When I was about to give up and go for a petrol or electric cars, I read about fuel additives. Wanted to give it a try. So bought a "Diesel System Cleaner", cleared warning lights, poured it to the tank when it was half-full, took it on the motorway for about 30 minutes.
Within 20 minutes I started noticing a great difference. Engine became very smooth, pickup and performance were fantastic, no more warning or fault lights.
So, if you are having similar troubles, give it a try. There are many brands such as STP, Redex, Innotec, Hydra, Liquimolly etc. I used STP.
Finally try to minimise the use of supermarket fuel as they seem to have higher impurities than premium ones.