Fear not Sir Gos but help us is on the way.
Like you, I'm a relative newbie at this--I still can't get Foobar to work properly but there are other ways.
In the case of Octopus, I have also experienced your frustrations. I was finally able to get it to rip properly by using MakeMKV to produce an MKV file (MakeMKV has a built-in decrypter so you have to temporarily disable any active decrypter, eg. DVDFAB Passkey for it to work properly). Within MakeMKV, you should make sure that you check only the relevant DTSMA streams. The correct one will have the appopriate number of chapters in its description of the DTSMA stream.
Then use Audiomuxer to extract the file and export it to flac (Audiomuxer -- Tools --" Extract Audio from MKV/MKA file". Check the "Export to Flac" and "Load in AudioMuxer and Split into Chapters boxes', set the Flac level if you wish (5 is probably the best), then click "Extract". Save the file to whatever directory you wish (the default name is output.flac) using the windows explorer window that will pop up if you haven't done this before. You will then be asked to tag the files. Once you have done this, press tag and audiomuxer will do its thing and eventually produce 9 output files in the case of Octopus (it will produce 10 if you do it any other way). You will then have to rename the files using a tagger (e.g. Mp3tag, I use Musichi).
To be clear, there is almost certainly nothing wrong with your usual method rather there is a problem with the DTSMA stream in Octopus. What seems to be happening is that a very brief lossy file exists in the DTSMA stream just before "Knots". The program is expecting a lossless file (as in DTSMA) and so screws up. What happens in MakeMKV is that very brief files (I think it is under 20 seconds) are ignored. Therefore it seems that the lossy (i.e. problem file) is bypassed and so does not make it into AudioMuxer for the conversion to flac and so AudioMuxer works properly.
Incidentally, you can use the MakeMKV/AudioMuxer combination for just about anything and they are both basically free (you get a 30 day trial for MakeMKV). Notice that I said 'just about' anything. Just now while ripping the very last of my Rock/Soundtrack discs, I found one that would not work using any method. It would rip the 24-192 2-channel layer but not the 24-192 surround layer. The blu-ray in question is Citizen Kane; The Classic Film Scores of Bernard Herrmann. It is produced by High Definition Tape Transfers (mentioned several times on this site). I will contact the company about this and I suspect they will send me or allow me access to the flac files that they also sell besides the physical disc; they are very nice people.
By the way, I find that the easiest way to rip these discs is to use DVDAE along with DVDFAB's Passkey (to decrypt the discs) because they are easier to tag using the metadata download feature of DVDAE. You can also use the "Extract from blu-ray" option under tools -- "extract audio from blu-ray" in audiomuxer if your disc is already decrypted with Passkey (or presumably something similar). There are many ways to skin a disc, particularly if you have all 4 programs (DVDAE, DVDFAB Passkey, AudioMuxer and MakeMKV.
Hope this helps.
Jim (aka J.R.)