getting double MKV files

[PeteS]

Why am I getting 2 MKV files when ripping 4K UHD discs? Same title on both one has t000 second t001 first one is a few bytes bigger.

[Woodstock]

Depends on the disk. Disney disks will have 2 or 3 copies, with each separated by the "other language" (English, Spanish, French usually) used in signs and such.

Without knowing WHICH disks you're having issues with, it's hard to say WHAT you're seeing.