I've got the 2B2QEXM7 firmware which is the latest for my drive. I tried to update it to 4B2QEXM7, but it seems the latter is for 970 EVO PLUS with another type of controller.
Thank you for the hardware diagnostics tip. I ran the test, the only issue I got was the "battery missing" (which I had previously pulled it out myself since it was swollen). So, the RAM works great.
Looking up for info on the internet, I found that the Samsung drives have issues with the controller. It is not optimised for MacOs, at least for Monterey.
I have now two identical MBP 15“ from mid 2015 running perfectly with the Samsung 970 EVO plus with the „old“ firmware 2.x…. Read/Write about 2.800.
I posted twice the reasons why Samsung switched from the „old“ Phoenix controller to that of the 980 Pro:
It was just because of pandemic-related productiin problems with the Phoenix controller, nothing else.
For further info just read the related two former postings in which I precised this.