As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SYR-DTW, DIVERTED TO BUF FOR RUDDER TRIM RUNAWAY. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT, EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE SWITCH WAS CONTAMINATED (APPEARED TO BE COFFEE ). CLEANED SWITCH AND RE-ADJUSTED THE KNOB TO WHERE IT IS NOT FLUSH ON THE PANEL MAKING IT GET STUCK, PERFORMED OPERATIONAL CHECK OF THE RUDDER TRIM, OPS CHECKS GOOD.