Failed to open last VOB file

I conveted a 4.4G MKV file with Convertxtodvd (which i have done many times) and when trying to use DVDSHRINK (which I have used successfully many times) it indicates failure to open the last VOB file.
This is the largest file I have tried to convert (never seen one with 9 VOB files).
Is there something wrong with the file or is DVDSHRINK unable to handles very larege files?

You can have up to ten VOBs in each VTS (numbered 0-9) so that’s still within the DVD specifications and shouldn’t be the problem.

Try running the output through FixVTS before processing with DVDShrink and see if that helps.