Intervention doesn't run on websites if streaming a video in full screen

I am having when I start an intervention and pick the duration on a streaming website such as Prime Video or BBC iPlayer, then I choose my show and click button on the video to make it fill the page, turning the video full screen (this is not the green top left button that makes Mac browsers full screen, I am specifically talking about any full screen video button that fills the entire screen on any streaming website).

Like this:

The problem is that the intervention will never play on that full screen, unless I click the button shown above on the video to minimise it. Meaning I can watch a 3-hour movie and not get an intervention despite setting it for 30 mins duration. Can this possibly be fixed, or is that not possible?