There are issues with GM's system as well....., not an uncommon subject on the GM truck forums.
Another possible area to check is the FW's brake wiring. On GM trucks the dash display for "Trailer Connection Status" is tied directly into the trailer's electrical brake system wiring only (not turn signals, running lights, etc.).
As mentioned a faulty FW (or TT, HTT, etc.) frame ground is a possibility, but a bad ground wire in the actual trailer brake system wiring can cause a 'fault', as well as a faulty brake magnet.
GM has gone as far as saying that the 7-pin connection "plug" from the trailer being towed should be manufactured by the same OEM that GM uses.