Alpha Channel Video Transparency not showing in finder preview or Quicktime

Hello

I've just jumped from Catalina to Monterey so I'm not sure where along the OSX journey that this feature was changed but...

I do a lot of motion graphics work and much of my work is delivered in MOV format (ProRes or HEVC) with transparency/alpha channel.

My final check before sending to client was always to preview the file in finder (using space bar for quick preview) or in Quicktime Player. The idea was, in preview, you could see a blurry translucency of your desktop through the artwork and in Quicktime Player, the background would be a dark grey - indicating an alpha channel.

However, since updating to Monterey, both the finder quick preview AND Quicktime player just show a solid black background. I know the alpha channel is there, but I do not want to have to reimport every video file to After Effects / Premiere etc to double check it before I send to client.

Is there a setting somewhere that can restore the older feature of seeing the effect of the alpha channel?

TIA.