Chamberlain Liftmaster Garage Door Opener Repairs. The chamberlain Liftmaster was amongst the best selling garage door openers in the world. They were a robust, heavy duty, garage door opener and many survive after 20 years or more reliable service. They are howerever still prone to faults. The faults can occur with the circuit boards, radio controls or the main cog drives. Where possible we will attempt to repair Liftmaster electric garage door openers and we have a source for the main plastic drive cogs that are prone to shredding, particularly when they are lifting heavy garage doors.