So I spend a few hours today trying to solve this exact same problem.
I was still on Android 5 1.0.9 firmware and decided to take the risk and upgrade to latest greatest Android 7.
Steps I took:
1. Upgraded via the upgrade instructions provided to 2.1.1 (via intermediate version 2.0.4).
2. Did a fresh install of Kodi 18.1
3. Configured Kodi and closed it.
4. Configured the wrapper to use the HiMedia wrapper player
5. Started Kodi again and added my NFS shares again.
6. Tried playing 1 of my 4K/HD-Audio files from NFS, black screen with VideoPlayer at the top, just like OP explained.
7. Switched back to original Kodi player, movie plays but with PCM audio, as expected.
8. Tried configuring the wrapper again, no success
9. Reinstalled the latest firmware using paper clip option.
10. Repeated all steps again, first on stock Kodi, then on latest. No success, same black screen.
11. Changed the profile xml in order to reflect the Wrapper option for NFS shares, no success with that option either. Compared the xml with versions here on the forum, no differences between them.
12. Downloaded the wrapper apk and installed it again, no success after reconfiguring the wrapper to use HiMedia player
13. After fiddling with different sources, it appeared that only my NFS shares were not playing, other sources worked fine. Double checked the playercorefactory.xml they appeared to be ok (Wrapper configured for NFS sources)
14. Decided to ditch the NFS config and move to SMB as a last resort before downgrading like OP did.
It worked!!!11!!!
Seeing that it used to work for me with NFS shares, it works for OP after downgrading to an older version it makes me assume that this is a bug in the latest firmware.
Bottom-line, by switching from NFS to SMB, the wrapper started to work again.