Electrical issue - haven't seen this discussed before

I've searched, but I haven't seen this come up before.  When I had my 7-pin connector wired, I asked them to wire the 12v power lead so that I could charge the T@B while driving (a 2018 320S Boondock, if that matters).  When I have the battery disconnect switch set to green so that I'm charging, my tow vehicle engine keeps running after I shut off the ignition switch!  Since it shuts off when I turn the battery disconnect switch to red, I assume they did something funky in the wiring and that the T@B battery is supplying power to my vehicle to keep the spark plugs firing.  Since I know nothing of 12v wiring, anybody have any ideas what they might have done?  I'll bring it back to the RV place that wired the 7-pin, but would like to have some info on what might be wrong.  Thanks!