iOS Safari html5 video autoplay takes longer than it did 6 months ago?

We have an autoplay .mp4 video of around 9mb that used to start pretty much immediately on iOS Safari like it currently has been on Chrome/Firefox desktop.

Since about 6 months ago it has taken around 1 minute before it plays (in fact before the whole page loads) even if we revisit the page after a few minutes.

Has Apple changed something regarding html5 video recently?

<video autoplay="" muted="" loop="" playsinline="" id="Video1">
   <source src="default-resources/video/video-003.webm" type="video/webm">
   <source src="default-resources/video/video-003.mp4" type="video/mp4">
</video>