As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW HAD A GEAR DISAGREE MASTER CAUTION MESSAGE. CREW FOLLOWED THE QRH PROCEDURES AND DECIDED TO RETURN TO CLT. THEY DECLARED AN EMERGENCY. MX INSPECTED AND FOUND PX18, RT MLG UPLOCK SENSOR FLAGGED. RERIGGED PX18 SENSOR. OPS CHECKS GOOD.