Huh. It's me the OP again. A year ago I sold the MS and got a 2016 MX P90DL.
And now it failed. Again BMS_w035 and a bunch of other errors. Vehicle unable to drive.
My insurance covers towing, so I ordered a tow truck. While waiting for it to arrive, I figured I'll connect a 12V charger to keep MCU alive so tow mode can be enabled etc
Obviously when the tow truck arrived, all errors were gone and car started fine. I actually drove it to the flatbed myself. I figured it's still better to let SC take a look, as it probably would fail again.
But I figured that perhaps it's the DCDC converter that's broken? After we charged 12V manually, DCDC doesn't need to charge and doesn't cause failure. Probably will fail again when 12V battery depletes.