well, the inverter would have nothing to do with the reading, or the chassis batteries, or anything from that angle, as it's only job is to 'invert'(change) 12v battery power to 120v power, for your outlets.
I suppose you simply have a 'stuck' readout - which is not either actually reading the voltage, or the screen for that particular portion is 'frozen'.... you may need to 'reboot' the computer, as they say...
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )