You can use a router or even a forstner bit to cut/drill out enough room on the bottom of the insert so that blade does not contact the insert before you raise the blade up through it. It may not take much since it may be only a few teeth that might contact the insert.
As for the glitch when lowering the blade, is it possible that it was always there there and you are just now hypersensitive to it because you had a problem.? Does it only happen when the blade is at max height or does it happen no matter what height you start at?
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.