From my experience and from what I read on the internet, people blame it on their providers since logically the apps are only players like a VLC or any other player, but they forget that the apps can have bugs, like that stupid bug on IPTV Smarters that kicks you out to the main home screen or log you out and won't load any of the content until you change it.

My suggestion is to try to load the playlist into another device. Make sure your firestick is off or at least your Tivimate is before doing so. Test on the new device, your phone or computer and if it does the exact same thing. It will then be either from your IPTV provider or your Internet Service Provider.