I have tried deleting the affected clips and re inserting and trimming them from the original file (which by the way is perfectly in sync) but that hasn't worked.
In addition I have tried producing a file of a particular clip and then inserting that into place. Whilst the produced file is perfectly in sync, as soon as I add it into the timeline of my other project the sync goes out.
Can anybody help? I have run a diagnostic file - not that that means anything to me, and can paste the results below if that will help.
Thanks, Jen