Do you run a 64-bit Avidemux build on Windows? If so, please delete all generated *.idx2 files in the VIDEO_TS folder, install the latest build of Avidemux (you have the choice between builds compiled with Microsoft Visual Studio on Windows (https://avidemux.org/nightly/vsWin64/) and those cross-compiled for Windows with MinGW on Linux (https://avidemux.org/nightly/win64/)), reproduce the issue, close Avidemux, then attach the log file admlog.txt from %localappdata%\avidemux\ to your reply.
Quote from: JohnnySH on November 02, 2020, 06:54:42 PMIf I then re nudge the start or end by a few frames and reset the A/B markers it will work ??
If modifying the selection leaves out spots where decode time stamps (DTS) don't advance (which most likely causes the failure to save the video), then this would be a logical explanation for this behaviour. The log file will hopefully tell.
MPEG-2 MPEG-PS streams like on DVD often have timing discontinuities midstream (SCR resets = system clock reference resets). Avidemux handles some, but not all cases of such discontinuities. I suspect that this might be related.
Quote from: JohnnySH on November 02, 2020, 06:54:42 PMoh... there is nothing wrong with the DVD rips
If the issue persists with the most recent build, it would be great if you could provide a small subset of the VIDEO_TS folder content using WeTransfer (no email address required!), Mega, Dropbox or Google Drive and exact steps (exact position of A and B markers, muxer configuration) necessary to reproduce the problem.