Do you have enable HW acceleration on dev settigs?
I had the exact same problem with a Philips android TV but I had just the best luck because I had 3 days left of the 2 years standard warranty. So I send it to service and changed the motherboard. basically the gpu from the motherboard was fried so more complex videos apps like Netflix or YouTube ar demanding to much of the fried gpu. I hope that is not your case buddy but I told you my story.
it's not matching the refresh rate of the specific app. you need to set your HDMI output in your android tv settings. If you're using HDMI 2.0 at 2160p, then set it to something like : YUV 422 12-bit Rec.709 YUV 422 12-bit Rec.2020
Activating game mode, may help.
Get an external streaming device. Sharp TVs haven’t been made in years, so the built-in apps are probably way out of date.