Did you stream it to the iPhone? Did you try downloading it to the iPhone and see if that makes a difference?
Downloaded version freezes too. Now this could either be an issue with the file or the app. I tried watching the downloaded movie in VLC but as usually it struggles to play (the main reason why I don’t use VLC). Any other apps I can use to play the file?
Sorry it’s taken so long to get back to you, with this being a file specific issue could you upload it so the devs could take a look and see what’s going on? You can upload it here.
Don’t forget to follow up with an email that references the file name. That will help tie things together.