Remux of a Blu-day video playbacks poorly (using tsMixer)

[HE1NZ]

My goal was to demux a film, add additional audio track and remux it back without any encoding. Using tsMuxer I did just that, but resulting video freezes when jumping on timeline and just works slow, crashes players. I tried doing this without subs, without audio, using different settings (SPS/PPS on and off, SEI and VUI data on an off, whatever they do). I also tried to encode it into mkv using mkvmerge. Result is the same. The original blu-ray film works great and is perfectly susceptible to encoding in Handbrake, but I don't want to rip it.

Please help, I'm new to remuxing stuff.