import failure Final Cut Pro X High Sierra

Since installing High Sierra, I have been unable to import video clips from my camcorders - both Panasonic into FCP. One camcorder is a HDC-HS700, and the other is a HC-X900.

They both make AVCHD files. I can see the files when I plug my camcorder in (via USB), or insert the SD card directly into the Macbook Pro, and I select the video clips I want to import. I can even preview the clips, but when I select the clips to import, it thinks about it for a while, showing 0% imported, and then finally, after a few seconds, it shows an import error message.

I have a Macbook Pro (Retina, Mid 2012), 2.6 Ghz Intel Core i7, 16GB RAM... I'm on macOS High Sierra 10.13.1

I can still import iframe video clips from the HC-X900, but the other camcorder only records AVCHD files. I can import them as MTS files, and convert them to mp4 files, and then import them to FCP... but this is a very long way around what used to be an easy process.

Any wisdom from the community?

Mike