All targets not being displayed.

I have ADS-B out using a Garmin GTX-330 ES transponder. I am using a Garmin GDL-39 for ADS-B In displaying on an iPad. Also the transponder has TIS which is displayed on the GNS-430W and a Garmin 396. I operating in the DFW area which has TIS info from the approach control radar and has several ADS-B sites.

I have noticed that not all of the radar targets that are sent to the TIS are rebroadcast and displayed by the ADS-B system. A Garmin rep at Oshkosh said they have also seen targets not being rebroadcast. Has anyone else observed this? How do you report this to the FAA?