UMK 3 (NES) - endurance fights?

[venixuc]

Ultimate Mortal Kombat 3 on the NES has 48 portraits on the select screen; all of them have to be fought in order to complete the game. However, this is not so straightforward - first 32 fights are normal and then the endurance matches take place.

You can see it in this video walkthrough (by Ryoga), skip to 37:17:

https://www.youtube.com/watch?v=MARRYWetj2M

After the cpu selects 33rd portrait (and every subsequent one), the Liu Kang/Stryker endurance matches have to be fought. And after the 48th portrait, there are 2 extra endurance matches - Liu Kang/Stryker (again) and Kano/Sub Zero.

The nuisance here is the fact that there are 17 Liu Kang/Stryker matches; so I'd like to change that by editing the rom and making other characters appear in the endurance matches.
The ram/rom values for the characters are:
Liu Kang - 00
Stryker - 01
Kano - 02
Sub Zero - 03
Sonya - 04
Shao Kahn - 05
Nightwolf - 06

Player 2 (cpu) values are stored at 00B7; starting with 33rd fight, this address shows only "BRK" in the FCEUX's 6502 Debugger. I searched the rom with "00 01" and found around 2500 of these value groups. Just for testing, I backed up the rom and changed all of them with "05 06", expecting to get the Shao Kahn/Nightwolf matches; but that didn't happen, all I got was the corruption of sound and graphics.
How to find the value groups responsible for these matches?