“This sounds like a Nissan Leaf problem”
Lots of documented happy 2012 Leaf Owners.
Nope, it is an Electric Car problem. Batteries can only be charged so many times and there capacity to take a charge diminishes with time. If too many cells fail (and they do) then it is too bad charlie. All Electric Car battery packs WILL FAIL with enough time and recharge events. It is a GIVEN.
Not only that but the manufacturer must maintain safety standards if they detect issues. Thus the battery pack of yesterday may not be available but only the revised safe one (which can cost more)
This was a 2012 model (would have been purchased in 2011). This is 2019 so the lowest number of years would be 7. This is about right for failures to occur with a normal to high rate of charging.
This is the Electric Car world. It is a GIVEN.