www.makemkv.com

I have the US 4K release of Aliens. The "Play All" option of the deleted/extended scenes brings up a sequence which is 7 chapters, 6:39 in length.

I looked all through the titles displayed by MakeMKV but couldn't find a match. When I loaded the whole disc as a source into HandBrake, however, I found the correct title (#152, 00869.MPLS) and was able to rip it.

Why would MakeMKV not display this title? I reduced my minimum title length down to 8 seconds, in case that had something to do with it, but that didn't help.

In the initial log screen (when you first open the disc/backup), is "00869.mlps" mentioned anywhere at all?

Sometimes MakeMKV skips a title if it thinks it's identical to another (even though it may not be), but for the most part, it usually lists most titles that it skips. Note that they may be out-of-order at the bottom of the list, too.

Can you get a segment map from Handbrake for 00869.mpls? If not, I believe you can get a segment map from MKVToolNix. Maybe MakeMKV is having a problem with one or more of the segments themselves?

If you can get a segment map, you could try temporarily renaming 00869.mpls in the backup folder to see whether MakaMKV then displays the individual segments, which you could then rip and join using MKVToolNix.