All I can add is a few commentsWith the top half of the tank removed and turret loose I would check all the wiring to make sure nothing is shorting out in the wires.Plastic does not conduct electrical current,to get a short it must be between wires or bare wires touching metal in some of the components.The top half of the tank is not neccessary to have hooked up to test the lower half of the tank.With the transmitter on and a charged battery hooked up to the tank and tank turned on you should have-flashing lights-push start buttonyou should have,sound,smoker,and all driving functions.When you plug in the turret connector,then all the upper functions.If there was a short in the upper turret wiring then it is possible that was what was causing all or some of the problems.
Why your tank would start up with the transmitter off is very strange===You may still have a major problem that exsists that may show up again.Just doing some guessing here,by no means an expert with tank wiring.But glad you have it going
BIGMIG