As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 4920 - THE AIR/GROUND FAIL MESSAGE ILLUMINATED DURING CLIMB AND THE CREW ELECTED TO RETURN TO IAH. MAINTENANCE REMOVED AND REPLACED THE NOSE LANDING GEAR PROXIMITY SWITCH TO CORRECT THE DISCREPANCY, PERFORMED SUCCESSFUL LANDING GEAR EXTENSION/RETRACTION TESTS AND CLEARED THE DISCREPANCY.