Videos play in slow motion - how to fix?

Videos in two paid membership sites I've joined play in very slow motion sound. These are videos hosted on the sites so they cant be played out of the browser on an app. Doesn't happen with YouTube videos or videos played in apps. But the two membership sites are not related to each other, so the problem would seem to be with my device. Plus, I did a factory reset which solved the problem for a day, but then it started again.

Any help would be appreciated. Please note that Im not a developer or particularly tech savvy. Thanks!