capacitors resist changes in voltage. So they are going to spark even when disconnected for a few seconds. The BORG has 00.000 amperes draw and .24 across the schottky at full song - both power supplies yelling at each other.
There are SO MANY WAYS to isolate a power supply it isn't funny...
Use a 120va tiny relay on the AC input to switch DC to a White Rogers, relay on the output.
Use a schottky rectifier and heat sink
Use a HD switch.
Well, time for bed. Early rise and shine. Tomorrow cross that line and face thousands of newly stoned California drivers...