I'm not sure if this is something normal or if it indicates a problem with the router. I recently put the 1/2" collet in, first time using that size collet, and used a panel pilot bit to route out door and window openings in 1/2" plywood sheathing. When running at full speed (6) the router was making a grinding noise, almost like the noise made when brushes are bad. When I lower the speed, the noise goes away. Even with the bit out and the router just running it makes the noise at full speed but not at a decreased speed. Is this something I should contact festool about, or does it sound normal??