Welcome to the forum!

It sounds like the internal wiring may be shorting out, powering the switch with the locomotive weight on it, or by wiggling the switch as you say.

Here is the wiring diagram of the 1121 switches:
http://pictures.olsenstoy.com/cd/swt/stc1121a.pdf

You may need to open up the switch to get at the wiring. That involves drilling out the eyelets, as shown here:
http://pictures.olsenstoy.com/cd/swt/stc1121c.pdf

Replacement eyelets, part #1550-8 are available here:
http://www.ttender.com/list/num6.htm


Larry