Xfinity Stream App Via Roku

I am having constant latency issues when using Xfinity Stream app. The mouth movements of characters on screen are not in sync with sound from tv. This requires me to go back to previous screen quite frequently to refresh picture. This “refresh” only works for a few minutes and I have to continuously repeat this process. This makes for a frustrating viewing experience and I tend to look at another streaming service altogether. This defeats the purpose because I am paying for a service that is not delivering a quality viewing experience. I have spoken to a few Xfinity reps but no resolution. The last rep told me I would be added to a national outage list as this is a known issue. I asked the rep how long the issue had been going on and I was told six months. Six months? This seemed like a very long time for an issue to be unresolved. Actually it’s been longer as I found after doing some research online. It’s been a month or so since I contacted tech support and I’m still having the issue. What do I have to do to get back to enjoying the service I am paying for? And there have been no refunds or credits for the months of unreliable service. Please help.