page works when disable cache not ticked

I have a page that is using a video element using videojs, with prebid, and google ad manager tags, with ima sdk. I’m seeing some weird activity. If i load the page I quite often get a “small black box” and the video doesnt load, on other occasions its fine. What I have noticed is that if I turn “disable cache” off in chrome consolue, it works 99% of the time, If I tick/ leave on disable cache it works 50% of the time. Would anyone have any clue why?

could it be anything to do with “headers” maybe?

disable cache on?
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disable cache off:
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