I am currently using a Roku streamstick+, however I've notice when watching 1080p conteng which means the Roku stick is upscaling the content to 4k, I get artifacts in the picture, such as faint horizontal lines about an inch apart going down the lefthand side of the screen.
Its not my tv causing the issue because I do not get these issues when watching the same content with the TV apps.
I've got no issues when playing 4k content through the stick. Just when it needs to upscale.
I don't think its an issue with roku stick, as I have had this same issue with another streamstick plus.