I tried the "revert to factory settings" and the "ctrl T" thing but same issue. It is an old win 10 workhorse laptop. Very slow by modern standards. So....have just tried on a much higher spec Win 11 machine.

The good news is that the sync issue has gone.

The bad news is that none of the three codecs supported by BIAB work.

However, I was able to open the avi video with VLC Media Player using the MS-CRAN codec.

Sean