Instagram videos not working in Firefox 52 ESR?

I've just noticed today that videos don't now seem to be appearing on Instagram pages with Firefox ESR 52.9.0.
There isn't even a placeholder, they are completely missing, all that's there of the posts is the text that should be beneath the video frame!
Static images are still displaying fine.
Is anyone else seeing this? They were fine yesterday!
The videos are still fine in Firefox 65 on Windows 10 needless to say.
I've tried spoofing the browser user agent using an extension, which I already have to do to get Facebook HTML5 videos to work, but none of the ones I've tried make any difference on Instagram.