punkalouver,
1/ Yes, TCAS was a causal factor, because, by the simple counterfactual test, had TCAS not been installed and working, there would have been no incident.
2/ Yes, there is a problem with TCAS.
So, it worked "as advertised". More precisely, it was found that it worked as specified. (Advertising is quite a different matter ...)
And that tells us that the problem is not so much an implementation problem. For all we know the implementation is adequate with respect to the specification. But, as we've been saying for years, there are problems with the specifications, as they do not (always) serve the intended purpose.
See Ueberlingen, where no reversal RA was given, although both aircraft were still closing. A modification to the specification addressing this specific problem is finally being mandated (CP112E, which, in an earlier form without the "E" (extended) has been on the table since before Ueberlingen).
This is old news. And this is a problem with only the technical part of TCAS. The wider implications of the entire socio-technical system TCAS/Flight Crews/ATC have been discussed at length in this and other threads.
'nuf said.
Bernd