Since replacing the 12 volt battery once seemed to produce a temporary improvement, I'd also follow that line of inquiry and check the voltage and, if possible, the capacity of the new battery. Maybe they didn't fully charge it before installation, and it went dead again?
Brilliant Silver 2021 Leaf SV40 W/ Pro Pilot & Protection
2009 Vectrix VX-1 W/18 Leaf modules, & 2 lithium E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.