Power supply disconnect sequence?

[Autosnap]

2024 2720QB New owner here, trying to learn. I tried boon-docking this last weekend in GSNP to try and learn my limits on battery power, and water tanks. I have a few questions. It didn't go well. Stupid issues aside...

I have the Ford tuck that has a generator on-board. so we used that to great effect during the day. I don't expect to do this all the time, but the trial on this part went swimmingly.

However, upon disconnecting the truck for quiet hours, we had no battery power. I had checked the panel before shutting the truck off and it said the battery was full. When I say no power, I mean, nothing, no lights, no water-pump, no info board, not even the gas sensor. TM was dead in the water. I checked all fuses, and breakers. There was no reason for it.

After thinking about it overnight, I decided to change the disconnect sequence. Well my 13y/o came up with this and I agreed as it is troubleshooting 101. So proud of him. He said, disconnect the trailer from the cable first as I had disconnected the truck first. It seems to have worked. I haven't had a chance to repeat this though.

My question is this, should this happen? I do have a soft start "Acustart".

Would the TM Board possibly see the capacitor in the soft start as the best source and negate the battery even after disconnected. Because I did disconnect the cable form the TM to store just after I disconnected it from the truck.

I'm pretty confused ATM... Thanks in advance for your replies.

Best,
Autosnap