[brazen1]

We understand many players and methods will play UHD HDR titles without actually engaging HDR mode.  Given PDVD v.18 and FAB v.5 are both performing UHD HDR for you and switching HDR mode on, evidently you meet the minimum requirements (at least for PDVD or it wouldn't be working).  Perhaps this is the key to get FAB v.5 working?  Please share which Intel SGX CPU, SGX motherboard, and Intel HD Graphics you are using.  Thanks.

Running Sky-lake i5-3600 chip with Nvidia 960. Gigabyte ga-z170x motherboard. 

 It looks like your CPU and MB do support SGX tech which meets some of PowerDVD requirements for UHD HDR.  Given that PowerDVD states

Ultra HD Blu-ray is supported only if a display is powered by Intel Graphics and supports HDCP 2.2. If your computer includes more than one graphics processor, Ultra HD Blu-ray is supported only on the display that is connected and powered by Intel Graphics.  https://www.cyberlink.com/support/produc...o?id=19881

I don't understand how your GTX 960 could be working unless you are actually using Intel Graphics and perhaps don't realize it?  In the event you are using Intel Graphics (which you must be since it is a PDVD requirement), it doesn't use private API's like nVidia and AMD do.  It uses Windows HDR which requires you to switch it on in W10 settings otherwise you won't have any HDR.  It's called 'HDR and WCG' after the last W10 update. 

I really don't know what the 'Stream HDR' switch in Windows settings does but it's greyed out unless HDR and WCG is enabled.  If it is enabled, and you leave it constantly enabled even when not playing UHD HDR video, you say it has no effect on quality.  On my system, turning on HDR and WCG switch makes the desktop unusable do to distortion but I'm not using Intel Graphics.  I'm using a GTX 960 because I want to use madVR with madVR players and I want to use PDVD and FAB as well.  If I upgraded to SGX hardware and Intel Graphics, madVR would no longer be compatible do to the private API HDR vs Windows HDR.

It fascinates me you are able to leave the 'HDR and WCG' switch always on as well as the 'Stream HDR' switch and have no ill effects when using the desktop.  This confirms my earlier suspicion that DVDFab Player v.3 uses private API's and v.5 abandoned that and now uses Windows HDR requiring the same special hardware and Intel Graphics as PowerDVD.  This explains why neither player works with nVidia or AMD and evidently only works with Intel Graphics for UHD HDR.  Personally, I will continue using DVDFab Player v.3 for HDR menus, PowerDVD v.18 for 3D menus, and MPC for quality main movie only of anything.  I can't give up madVR.  I'm hooked.