How many hours on your collet? It may be time to replace. Take it out, clean it well with steam, inside and out. Make sure you get between the flutes as well. Dry with compressed air. Inspect the internal bore under a microscope for and grooves or wear. If none, clean the internal portion of the spindle really well with q tips. LIGHTLY grease your collet as shown in the owners manual, reinstall.
Hey CHL, yeah I've been a bit of a ghost lately, covid hit hard here. Focused on other passions but dental keeps calling me back, guess I'm a lifer . Starting a new in house lab for a group of doctors, should be running in a few weeks.