As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPT WX RADAR TILT CONTROL DIAL DOES NOT MATCH ACTUAL TILT SHOWN ON ND FOR WX RADAR IN MANUAL MODE ON CAPTAIN'S DISPLAY. GROUNDED - YES. FOUND SHAFT OF CAPT'S TILT KNOB LOOSE. R & RD WX RADAR CONT PNL PER B737-800 AMM 34-43-91. SYS OPS CKS NML PER SAME. GND VERIFICATION SUCCESSFUL.