I have dropped my chain twice in the last 3 days as I have shifted to the big chainring. I recently had the bike into a shop where they took the front derailleur off and put some grease under the clamp in an effort to silence a mystery creak. I wonder if the derailleur was reinstalled incorrectly. How much space should there be between the bottom of the cage and the teeth of the chainring? Right now there is about 2mm.