I am also having the same problem. When updating settings in Camera Raw, 'Error' message appears, 'Unable to save raw conversion settings There was an unknown error' When reopening image in Camera Raw the settings have ,in fact, been saved. However, when I attempt to bulk update through Bridge the Error message re-appears & no images have been updated.
CC2018. iMac Retina 5K, 27" 2017, OS High Sierra, 10.13.1
My folders are Read & Write activated. Have had no problems on older Mac CC2014.