It seems like the version number it is not specified in the info about Safari on the iPhone’s settings, but according to what I could Google, the Safari version correlates to the iOS version, thus:
iPhone 11 - iOS 15.6.1 - Safari 15
iPhone 15 Pro - iOS 17.0.3 - Safari 17
I have now also tested the website in these configurations with the following results:
iPhone 11 - iOS 15.6.1 - Chrome - NO BLINKING
iPhone 11 - iOS 15.6.1 - MS Edge - NO BLINKING
iPhone 15 Pro - iOS 17.0.3 - Chrome - BLINKING
iPhone 15 Pro - iOS 17.0.3 - MS Edge - BLINKING
So it must be an iOS 17 issue then.
Another note: If you look at the three testimonials of the start page, or the three testimonials on this page: https://shootit.se/matfotograf-i-orebro it is only the first columns that blinks after the animation has loaded, not the second and third column. So it seems like it is the first object in every row?
I have now also added the code from @raye to the first testimonial column, the image with grey logotypes and the green button. (on this page https://shootit.se/matfotograf-i-orebro). The only difference is that the first testimonial column now blinks in a slightly different way, half of it gets some kind of overlay for a short moment. See screencapture here:
https://www.shootit.se/download/blinking-elements-2.mp4
The image with the logotypes and the green button blinks the same way as before.
This is the way I added the code, is it the correct way to do it?
Any ideas for a solution, or what could be causing it?