Issues with gallery slideshow block - auto transitions on Android/windows

Hello, I am having an issue with a gallery slideshow block on a client site (I dont have an example to show unfortunately because I had to remove it from the live site due to the transition issues).

But I had previously created a portrait size gallery block on a section on the site, which had about 7 portrait photos in the gallery. I chose "auto transition", and 5 seconds between, and no arrows.

And when i tested it, it worked fine on my apple iphone, ipad and my mac, but on windows or android devices, instead of transitioning between the photos, it was showing a faded white screen for 5 seconds or so (like it was another photo almost) and then transitioning to the next photo. Almost as if the transition was really slow.

I tried to troubleshoot and change some settings and no luck. 

Any idea why this might be happening? I have another auto-transition full screen slideshow on the page (landscape) which is working fine. 

thank you! Jules 🙂