if your brakes are going on while the batteries are unplugged. Then it sounds like a short on the 3 phase motor wires.
Anytime you touch 2 of the 3 motor wires together it makes them brake even if they are disconnected from the system.
Try disconnecting the motors and spin them by hand, moving the wires around as you spin them and see if the brakes come on.
I just don’t see how the problem could be the receiver connection if it happens when the batteries are disconnected.
The vesc lights up when coasting so there’s some electricity doing something in there. I thought it was maybe just me and I was delusional but after its happened now repeatedly as I repeatedly break receiver connections I’m sure. Batteries unplugged, motors work fine, brakes slam on with bad receiver connection randomly
yeah the VESC has a dead man switch behavior if the controller is turned off.
The motor will still turn but a lot of resistance if I turn off my GTB.
Probably a good thing if the rider falls off then the board will try to slow down and not just rocket off a cliff or into a curb.
I use that feature if I want to walk away from the board to press a crosswalk signal etc and when I turn off the receiver it acts like a parking brake when I walk away.
Think I would just solder the signal wires to the Vesc but another thing you can try, if you don’t want to solder them, is to bend the plug pins on the Vesc a little so that the connectors fit tighter.