www.makemkv.com

I know this has been asked many times before, but I'm still worried so I need to ask again for reassurance.
In the past, I backed up my DVDs to ISO files using MakeMKV and the process completed successfully (ISO were created). However, I don't remember if there were any warnings or errors during the backup process at that time.
From what I've read online, if there are errors during the backup process, MakeMKV won't create an ISO file (or will fail completely).
My question is: If I have an ISO file that was created by MakeMKV, can I assume it's a 1:1 bit-perfect copy of the original disc?
I no longer have the physical discs (sold them), so I have no way to verify against the originals. I just want to confirm that the ISOs I have are complete and accurate copies.
When I open these ISOs in MakeMKV again now, some show "Operation successfully completed" with no errors, while others show "Operation successfully completed" but with "Calculated BUP offset for VTS #X does not match one in IFO header" warnings.
Does the presence of these BUP offset warnings mean the ISO is corrupted or incomplete? Or are they just authoring quirks that were copied from the disc?
Thank you for your help!

I would presume the copies are fine.

The BUP messages are the same as you see on the original disc. Something screwy with the workflow of the original disc authoring, but not fatal.

If you decrypted the data during the copy process, then of course the copies are different from the encrypted material that was originally on the discs.

I do not know how MakeMKV handles errors during DVD copying, but it would have to depend on the optical drive reporting read errors. Some drives do not do that. MakeMKV does use hash information from blu-ray discs that have it, so the integrity of the copied information can be checked. DVDs do not have hash information on the discs.

I use DVDFab for DVDs and copy each DVD twice. I create a hash file for the first copy using hashdeep, then audit the second copy using the has file. That will catch inconsistent reads. That still leaves the question of the copy software (DVDFab or MakeMKV) skipping elements on the disc that you do not want skipped. MakeMKV tends to skip "short" video files, menus, etc. unless you use the full-disc backup. So I only do full-disc backup, and almost never select bits and pieces to construct MKV files, since the extras and menus on discs are worth preserving.

Thank you everyone for the helpful responses.
After testing playback on all my ISO files, everything plays without any issues, so I'm reassured that they're fine.
Going forward, I think I'll switch to buying Blu-rays instead of DVDs, so I can verify using the content hash table and keep more careful logs of the ripping process.
Thanks again for the advice!

Once you ripped every extra video, one wouldn't really need the structure anymore, I would have thought.

I do know, that a very few DVDs place extra videos within the menu part of the disc, which MakeMKV cannot make a video from, but I have only like 1 or 2 DVDs with that.