Help me understand missing traffic w/MLB100

For context I have an AXP322 for ADS-B 1090 OUT, and an MLB100 for 978 IN.  I also have L3 Skywatch TCAS in my plane, so I have the luxury of comparing TCAS traffic with ADS-B traffic.

What I've been seeing is LOTS of traffic that I can see on TCAS, but I never ever see it on ADS-B.  My understanding is that my setup should:

A) Receive direct reports from aircraft equipped with UAT/978 OUT hardware.

B) Receive ADS-R rebroadcast traffic from ground stations, for 1090 targets since the MLB100 doesn't have 1090 IN.

C) Receive TIS-B traffic from ground stations, for Mode-C targets that aren't participating in ADS-B.

So my question is, why do scenarios B and C seem to not be working for me?  Are the ground stations really unreliable?

I requested an ADS-B Performance Report for one of my flights this evening where this situation occurred multiple times, and I see two important things:

A) OUT capability is correctly listed as 1090 and IN capability is listed as UAT.  This should indicate that the FAA systems know I need 1090 targets rebroadcast to me.

B) TIS-B Client % is listed as 94.5%, which should mean that only a very small portion of my flight would have been a "dead zone" for ground station traffic.

Any ideas?

I'd have to go double check but I do know that when I had the IFDs updated to 10.2, they made sure the connection on both ends was in compliance with the service bulletin relating to setting the protocol correctly.  I believe that was for the RS232 connection between the devices.