Prime streaming unsyncing--anyone else having this issue?

It happens every time we rent a video on Prime--there are lags, it falls out of synch, and we have to do a restart with our Firestick. By the time we get to the end, we've adapted and it stops driving us so nuts. Until the next time!

Now it has started happening while streaming series. Not as much, but enough that we notice.

I thought it might be our wifi, but it doesn't happen with Netflix, Kanopy, or YouTube.

The first time it happened with a rented movie, I requested a refund. That was a lot of work to get $3.99 back, and they said it was only a one-time courtesy.