[Shield] Not showing videos in 4K HDR

After all the problems with my Philips Android tv (never, ever again Philips untill they make stable software), I decided to sell that thing and changed it into a Loewe One 55 with a SL412 chassis. This means that this Loewe supports HDCP 2.2 on every HDMI input and since the last software-update, it supports HDR10 and HLG. I combined this Loewe with an Nvidia Shield 2017 for a good Android experience

I possess two test movies from Sony and LG for demonstrating HDR. With or without HDR the picture quality has huge differences.

So, connecting a HiMedia Q5 mediaplayer, played back the movies and my TV shows the nice HDR colours. In the OSD of the TV is the message “HDR10” seen. So clearely my TV supports HDR via HDMI.

Playing back the same movies on the Shield, no HDR at all.
I use the same settings as the HiMedia uses (4K59,9, dynamic range=full).
Both Kodi and SPMC refuse to show HDR.

What could be the problem?

Thanks
Gert