The RFM Damper Knob Assembly (FT96AS on MO22) has a threaded insert, which VOC Spares calls FT97 (not shown in any spares manual that I know of). Can someone tell me how the insert is removed and replaced, please? On my knob, the insert is broken such that several of the detents are missing. I would like to replace it without damaging the knob. Thank you.