Hope this hasn't been posted already yet.
Since the latest CO update I have some major problems with RAW files of my Canon EOS R.
First, I am completely unable to import new files to CO (RAW files aren't recognized in the import window although they are "physically" there in the selected folder).
Second, most of the RAW files, which I have imported earlier, get an exclamation mark warning sign in CO and are blocked for editing. It looks like this:

It does show a very low-resolution preview of the image only and all control elements in the toolbox are blocked. The browser doesn't show any preview at all. However, this does not apply to all images of this set. Very few of them (<1%) are still working normally. I was unable yet to find a pattern why these images are still okay. (All other photos of the catalog, shot using different cameras, are working fine.) Plus, this whole thing only happens, as soon as I connect the NAS where the original RAW files are stored. In offline mode, all photos show fine with their offline previews, although editing tools are still blocked (which is also odd).
All these problems appeared after the update to CO 12.1 - prior everything was fine. Does anyone have a similar problem? Or maybe a solution already?
Rebuilding previews doesn't work - it seems to have no effect at all since it doesn't really build a new preview but skips every photo. Original RAW files are available on a NAS, works for all files of the catalog except for the mentioned ones. I am quite sure that there is no damage to the original RAW files on the NAS, since until the CO update everything was working well. I'm using CO Pro 12.1 on a MacBook Pro Late 2013.
Thanks and best regards!
UPDATE: It seems that some of my EOS R photos got removed from the catalog as well.