As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURN, UPON CLIMB AND RETRACTION OF THE GEAR THE PILOTS REPORTED THAT THE LT MAIN GEAR WOULD NOT RETRACT AND A GRINDING NOISE WAS HEARD. THE GEAR THEN EXTENDED NORMALLY. MX WAS DISPATCHED AND FOUND BOTH LT UPLOCK SENSORS LOOSE. MX TIGHTENED AND ADJUSTED SWITCHES IAW MM 32-60. OPS CHECKS WERE GOOD.