Im thinking chassis battery since the low voltage warning corresponds to the voltage gauge on the dash (chassis battery). That voltage regulator is weird... Ive never seen a gauge that acts like that... I usually don't do anything unless the voltage is above 13V, anything below that... electrical warnings starts popping up. Happened when my wife put it in DRIVE and low voltage warning came up... she did this while the voltage was below 13V.
2014 Thor Palazzo 33.3 (Melody), Folkstone
2017 Jeep Rubicon, Ready Brute Elite & Currie Ent Baseplate