www.makemkv.com

Will I have an answer, please?

I dont understand your suggestion

You mean record small file?

Why?

I have different disks and all with same error, and only if multiple titles identified. And all of them are playable fine

It doesnt look like corrupt files, rather inability of the program to correctly process multiple titles ...

Why it takes so long to get answers?

Opened fine, no warnings, here is the log:

MakeMKV v1.6.4 win(x86-release) started
The new version 1.6.5 is available for download at http://www.makemkv.com/download
Opening files on harddrive at D:/Home movies/Family/1 Архив ДВД 2000-2010/Дети/Дети 1 февраль 2000 - декабрь 2003/Диск 6 15 сентября ...

That means that IFO files are incorrect.

How did you author these discs?

Does it work if you open IFO file from disc via File-Open menu and ignore warning?

Well, disks were burned and finalised by standalone recorder

Now I copied disks to HDD and intended to convert them to mkvs (my media ...

I burned the disks by myself, so I dont have spare one to swap. All DVDs are readable and copiable OK - actually makemkv works with disks contents, already copied to HDD

ALL of the disks where only 1 title was identified by program, were converted fine

ALL those where 2 or more titles we found ...

Anyone?

I have copied bunch of my home video DVD to the HDD and then tried to convert them into mkvs

Majority worked fine (1 title identified), however few of them, where MakeMKV identified 2 or more titles, I got error -

"The source file ХХХХ is corrupt or invalid at offset NNNNNNN attempting to work ...