Importing AVCHD (full HD Video)files to FCPX

Using a Sony FDR AX100 camcorder, I can record AVCHD files to the camcorder, but when I try to import them in the normal way to FCPX the sound is missing. I have just experimented and I can import an AVCHD file to my apple photos application and it looks completely normal. However, if I then export it to the desk top and try to get FCPX to import it FCPX gets hung up, working hard with fan on full blast but no progress in "Transcoding and Analysis" or "Analysing Audio" progress bars in the background tasks window. So evidently something wrong with FCPX settings since AVCHD files imported to photos no problem...

Have had a look at previous posts here about the old A52Codec.component files and have scoured my library and quicktime folders and cannot see any trace of such a file.

Any hunches...? Have just discovered an online article describing known incompatibility of AFCHD files with FCPX...will have a look at those and report back! ...of course I can use Sony's codec XAVCS...

FCPX = 10.4.10

MACOS = 10.14.6