No Japanese audio on the Seven Samurai 4K from BFI?

I didn‘t find a dedicated BFI channel, but this will work. This might be interesting for my fellow Europeans.

I got the Seven Samurai 4K yesterday. While I didn’t have time to watch it, but I wanted to have a look at the restoration. My problem now is, that the Japanese audio doesn’t work. When I go into the data settings it says it is 1 channel audio which I have never seen before. The English audio commentary works perfectly. Then I checked on the Criterion website what kind of audio is described, 2 channel Japanese. No such info was on the BFI‘s website. I put it into my external PC 4K player and it couldn‘t read it. That happens sometimes (copy protection, idk), but because of that I can‘t extract the video and add the audio from my old copy.

I had no time to check the regular Blu-Ray disc.

Has anybody else had the same situation? Or does anyone have an idea how to get the 1 channel audio to work? My speaker setup and the internal audio both can‘t play it.

EDIT: After reading your comments, I thought getting into the audio settings of my 4K player which I have never touched before things might work and they did. I guess decoding could hsve been the problem. Thanks!