Which levels of the preview have dolby vision

Everything is fine, you still get 4K and HDR just not Dolby Vision which is just a branded version of HDR. There really isn't much of a difference between HDR10+ and Dolby Vision, personal preference just like Dolby and DTS audio.

I am using Pioneer VSX-832 audio recevier, as far as I am aware it is updated already. Microsoft claims both can be turned on, which I can, but then Dolby Vision only works and hdr 10 don't. Also, Dolby Vision only works correctly when only Dolby Vision
is turned on.

Hi o all to be honest is not impossible to do Dolby Vision on all the Xboxone and the reason is very simple. The real benefit of Dolby Vision is that it doesn't need the new HDMI 2.0 standard to work. 'Regular' HDR10 signals do need
HDMI 2.0, a standard that only the latest kit has. Because Dolby Vision can operate with HDMI 1.4, its potential applications are much greater, which is very good news. http://www.pocket-lint.com/news/140385-dolby-vision-is-now-available-as-a-software-update-to-upgrade-compatible-kit

Hi

If your console is up to date it should work.

Xbox One Dolby Vision HDR - Everything you should know:

https://www.windowscentral.com/xbox-one-dolby-vision

How to use Dolby Vision HDR on Xbox One:

https://www.windowscentral.com/xbox-one-enable-dolby-vision

I found people having these problems, but I can't link the URLs here because they don't really have any fix for it (instead of just disabling Dolby Vision or HDR) and are not from Microsoft community or official websites.

It's not a "problem" with your console but it is indeed a bug.

Unfortunately there's nothing we can do except disable Dolby Vision, change your HDMI cable/port or maybe contact your TV manufacturer. If you could test it on another TV which also supports Dolby Vision it would be great, but it's not really feasable.