How to fix sync sound issues in iMovie projects?

OK, no replies here but I've investigated my problem for the last few weeks and this is what I've found: All Projects sourced from MEDIA dated between 2004-2010 (but imported into iMovie from 2009 onwards) has this problem. The sync sound does not play properly with either no sound, then the sound may play for a moment and stop/start again - hopeless (the video image itself plays normally). The MEDIA itself also displays this problem when played independently of any project. We had an iMovie update on 27 June 2024 and this is when the problem started. Everything was working fine before this date. I've thus identified that all the now faulty material was recorded on a 2004 Digital Tape Canon movie-cam. All other material from other cameras and professionally digitised film (Std and Super 8) sourced from content filmed from 1959 onwards play correctly (all footage being imported into iMovie since around 2009). My guess is that an audio format was knocked off the list by Apples latest update. I stress that iMovie and all MEDIA and PROJECTS were 100% fine around 23 June. I post this in case anyone else has had a similar problem and hoping that Apple investigates.

Incidentally I have "Voice Enhance" selected for many of the affected clips.

Sorry, just an update on the movie-cam: It's a Panasonic NV-GS11 Digital Video Camera.