Adobe Spark Page

yes. I see the problem in your video.

In the Safari browser, it takes a very long time to load.

I don't use as many YouTube videos in my pages. Perhaps it is waiting for YouTube to populate the thumbnails of each video? 

I just updated my Spark Page iOS on my phone, and it seems to be working well.  I am using WiFi and have a very strong/fast connection.

I hope a Restart of your phone, or update of the software will fix the error for you.