Pairing the 2x 26650/18650 batteries is definitely needed in flashlights.
The next mode memory situation can be fixed with a difficulty of 1. I’ll look for the thread with pictures.
Unless you want to replace the 5 modes as well, then you’re looking at a 2-3 difficulty in a driver swap.
The switch issue… Could be a few things. The couple of my lights that did it were due to weak springs that caused contact issues when the light is fully tightened. I just lived with them being 1/2 turn from fully tight and the flickering is gone.