As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOTS REPORTED VERY WEAK NAVIGATION RECEPTION, EVEN AFTER NUMEROUS CHECKS FROM AVIONICS SHOP EQUIPMENT. A DIFFERENT SET OF ANTENNAS WERE INSTALLED, BUT DID NOT RESOLVE PROBLEM. ONLY AFTER A NEW SET OF ANTENNAS WERE INSTALLED, DID THE PROBLEM DISAPPEAR.