How does DVDfab choose .MKV or .MP4?

[SG_Fab]

I have converted my entire 4K UHD library now using DVDfab, however when I used the Ripper, most of my movies came out with a .MKV extension which I expected but others ripped with a .MP4 extension.
Can anyone explain what the differences are with the disc content that makes DVDfab choose one over the other? I used the same setting on all of the rips.

[signals]

If you used the same settings, they should be the same. To help you we will need more information including DVDFab internal logs and the name of some titles and which way they convert.

Moving thread to the UHD Ripper forum.