The electric brakes on you trailer have two power sources. The trailer brake controller on your dash and , through the safety wire break away switch they are fed full trailer battery voltage to lock them up if the trailer becomes separated from the tow vehicle. Always hook the safety/ break away wire up to the tow vehicle before you move, and always tow with the trailer battery hooked up and charged.
Yes , bad propane valve.
BTW, Welcome to iRV2.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.