We have had and still do have many TCAS problems on our 737 fleet (also Allied Signal). The Boe rep here tells me there are 2 systems avail on build, the good (expensive) one and the one we have.
After many antenna and processor changes, all of our problems to date have shown to be cable trouble. From badly routed cables putting strain on connections to finding connectors only slaved on and not crimped, we have seen just about everything and nothing surprises now.
Think I'll go for a job in Boeing QA coz I could do with a job where I get paid for doing nothing!!