I got a Streaming Stick+ (maximum 4K resolution) in August to use on a 1080p TV. I chose this model for its codec support on Plex. From the start it's had audio sync issues that range in severity, with Prime Video being the worst offender and Plex coming in second. Disney+ is more mild but still noticeable, and it varies at times. I use my TV's built-in speakers.
Today I borrowed a Roku Express (maximum 1080p resolution) and the audio sync was perfect on every app. Following this, I connected my Streaming Stick+ to a 4K TV, and the sync was perfect on there too. I then connected the Stick+ to a different 1080p TV, and the audio was out of sync again. (Sorry if this is a little hard to follow!)
I can only conclude that the issues with the Stick+ arise when it's not operating in its native resolution on a 4K TV. The Roku Express has a maximum resolution of 1080p and works just fine.
This is a strange issue, I figured that the Stick+ would be fine running in a lower resolution but clearly it's not. I have tried tinkering with a multitude of settings but nothing seems to make any difference.
My TVs are not 4K either. And it’s interesting because the sync problem comes and goes sometimes even within the same program. Sometimes after a commercial, the syncing will correct itself when the program comes back. Program I was just watching was on an app. My Internet connection is Spectrum, but I wasn’t using the spectrum app. I think the synk lag Problem happens On other apps like Netflix or prime. It doesn’t happen all that often. So it could be the spectrum modem my Wi-Fi modem which is separate my spectrum modem. Or it could be the way the program is being broadcast. It’s often same program when I see it happening. I just don’t know the answer to that.