Keep encoding when request is handled by irule

I have custom irule to check data in payload. I noticed issue when non-latin characters are detected, for example Japan characters.

In this case seems that byte array is not read correctly (2 bytes vs 4 bytes) what just corrupt/change payload. I am almost sure that I hit follow: https://my.f5.com/manage/s/article/K22406348.

There is mentioned option to use binary scan but does not work for me. In generally I do not add anything to payload or modify it. I just compare some properties and block request if it match condition.

How I can keep origin payload as it is?