Electrical Gremlin?

Everything going off is most likely the service disconnect ( male/female connector ) at the firewall.
The top switch wasn't so inadiquate when the car was new. Age , use, increased amp draw caused by a top frame that doesn't move as easy as it one did, all this takes its toll on the original electrical components.
If that wiggling the top switch makes a difference, that switch may be partialy closed and bleeding a small amount of current. Not enough to run the pump motor, just enough to keep it nice and warm. Warms the forementioned connector also.
To replace everything with new OEM components will likely work for a long time.
Adding realys, larger, wiring,etc.. to the top circuit might be a good plan but relays and everything else under the sun will fail eventually.