Should I not buy a 2017 or 2018 grand Cherokee due to poor reliability rating for example engine electrical transmission ?
You can buy whatever you want. I personally would not touch a Jeep product of any kind. They all seem to have a case of the 'Fiats" since being taken over by Italian carmaker, Fiat. Fiat also owns Alfa Romeo, BTW. So 3 of the worst 7 are Fiat brands.
I would question why such an expensive vehicle was on the market so soon. Someone had to take a big financial hit to get rid of it. Now a 2016 might be a lease return . But if you are on a forum asking if you should buy a certain vehicle then maybe you should look for some thing that does not cause you concern.
Lot of red flags here. IF you do buy it, be certain you have a solid understanding of the warranty that is included and I would suggest looking closely at the service records.
So statistically the odds are this car would break down more often than a similar car from other maker. But, you can also get a lemon from other makers.
Do you feel lucky?
The question is how badly you want the Jeep.
Once, I asked on the Chrysler forum if they would recommend a used Jeep as a replacement for our Minivan. Even the long time Jeep fans advised against a Jeep.