Denon AVR-X2600H video output problem with TV Tuner HDMI input source

Denon AVR-X2600H video output problem with TV Tuner HDMI input source
Recorded on 2020-03-09.

UPDATE 2020-03-11: I connected the TV tuner via ANALOG connections (composite video + analog audio) and got the same result - audio works but no video. Very puzzled!!
Also tried connecting via the FRONT HDMI port which Denon USA (Sound United) suggested and got the same result.

Problem experienced with both of these digital TV tuners:
1. Ei8ht EHD768 (Eight EHD768)
2. Prima PM-3030RM
Both TV tuners have no issue when the Denon is bypassed and output directly to Samsung UA60D8000Y 60" LCD TV or Optoma UHD60 projector (also through HDMI matrix/switcher).
Also tried adjusting video output settings on the TV tuners (e.g. 1080i, 1080p, 720p, Auto aspect ratio, 16:9 Widescreen...) but with no difference/improvement.
Denon is running latest firmware and works perfectly with NVIDIA SHIELD as input source but just not with the above TV tuners.
I first recorded a video of the issue here (unlisted): https://youtu.be/Mp1Zb5w_adM

Any suggestions to get resolve this issue would be greatly appreciated.
Thanks for watching.

Видео Denon AVR-X2600H video output problem with TV Tuner HDMI input source канала Derek Tom