Thanks for the info guys, below is the a screen grap of what mediainfo says about each file:-
This plays audio but blank screen on Duo4K
Screenshot 2024-04-05 202357.jpg
Whereas the Duo4k will play this file correctly
Screenshot 2024-04-05 202459.jpg
Both of my Uno4Kse's play both files correctly.
Appreciate the help, perhaps I should have waited to buy a Duo4kse............
I'd like to add these files were not for me but the Mrs............