loose contact with line driver card?

Following up my previous post, going through the diagrams, it appears that the only thing between our injected signal and some of the equipment is the line driver cards. Going through the line driver cards, tracing the signal since the circuit diagram could not be found, apparently no path for the System Reset signal there - just a dumb buffer using UHP 407s with pin 8 just connected to Vcc. So, system malfunction most probably due to a loose card, rather than anything else.