What was found
AIRCRAFT WAS GROUNDED: AUDIBLE SQUEAL HEARD COMING FROM DOOR 4L. SD SCREEN SHOWS 4L SLIDE IS NOT ARMED BUT FLIGHT ATTENDANTS CONFIRM IT IS ARMED. THIS CHANGED STATUS SOMETIME AFTER TAKEOFF. CABIN PSI DIF: 7.9, CABIN ALT.: 6,450'. CRUISE ALTITUDE: 34,000'. MAINTENANCE FOUND STRAP OF DOOR SLIDE (4L) BUSTLE PINCHED BETWEEN DOOR AND FRAME, SECURED STRAP AND PERFORMED PRESSURIZATION TEST PER AMM 05-53-00 WITH NO LEAKS OR AUDIBLE SQUEAL NOTED, MAINTENANCE ALSO PERFORMED A SATISFACTORY OPERATIONAL CHECK OF THE DOOR ARMING SYSTEM PER AMM 52-73-00 WITH NO ISSUES NOTED.