Media Texture not displaying Media input UE 5.3.2 and 5.4.2

Hi people,
I’ve created a media profile and added my Blackmagic Decklink 8K Pro as the input and output. Both connections have been tested in BM’s Media Express app. Media Player will display the incoming video signal fine, but the Media Texture does not. It just stays black with a 2x2 pixel image size. This means that I cannot use the Media Texture in my Media Plate layer, in Composure.
I tried turning on the Electra plugin, as suggested elsewhere, but it doesn’t work. It freezes the Media Player input or simply turns black again and I can’t restart it.
This is a MASSIVE issue and not a simple ‘bug’ if I can’t create a live layer in Composure.
Anyone found a fix?
Thanks.

5.4.4 also has this problem

Cheers! need set BlackmagicMediaSource “Just-In-Time Rendering” is false