As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS-FLIGHT#3852. CREW REPORTED AIRCRAFT ACCELERATES WHEN REVERSE IS SELECTED. MAINTENANCE VERIFIED BETA BACKUP SYSTEM IS ENGAGING, AND REPLACED BETA BACKUP POWER LEVER SWITCH 6141-S3. AFTER TAXIING AIRCRAFT, OPERATIONAL CHECK WAS GOOD. AIRCRAFT RETURNED TO SERVICE.