I noticed this when loading the aircraft at KPDX after my initial update to 18.104.22.168
Manually tuning VORs works fine. However, if I go back to auto tuning by clearing the manual entry for either NAV1 or NAV2, the frequency in the FMS page shows "16666.67"
The same thing happens if I do not make a manual entry - i.e. if I leave the NAV receivers set to auto tuning when loading the aircraft, it will automatically tune to the closest VOR. Example, when loading at KPDX, the receivers automatically select BTG VOR on 116.6 - but as soon as I fly out of range, (when the FMS would normally select a different enroute VOR), the same "16666.67" appears on the RAD NAV page, and no further automatic VOR tuning takes place. Going back to manual tuning does work with no problems.