As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB AT 10,000 FEET, THE CAPTAIN'S SLIDING WINDOW DEVELOPED A LOUD SQUEAL WHICH PROGRESSIVELY WORSENED UNTIL COMMUNICATION BECAME DIFFICULT AT 28,000 FEET. RETURNED TO MSP WITHOUT FURTHER INCIDENT. FOUND THE SLIDING WINDOW PANE TO FRAME SEAL DISLODGED IN THE WINDOW ASSEMBLY. REPLACED SAME, PRESSURIZATION CHECK OK.