Tanner,
I'll make this easy for you to finally push this up to the Roku developers to fix this BUG in either the 3910RW-Roku Express+ or the Roku Media Player.
First, the problem. My viewable movie also looks like the screen pictured in the 11-05-2019 image posted. Much of the video to the right and below is simply cut off, but the image is also shifted left a little. When I first played a video, it worked perfectly and filled the screen. I moved around the menus and played a second video. After I pressed the home button and tried to launch the Roku Media Player again, this image resulted and can not be fixed.
I've attempted to fix it by resetting it, unplugging it, go into the secret menus cycling and resetting everything making sure all software was up to date, and trying different display types. I've done everything short of factory resetting it which isn't a viable fix anyway.
My connection is composite 4:3 to the video-in of an older tube television. Of course the model of the television is irrelevant since it is analog composite sent out the Roku 3-phono plug composite cable. There is no HDMI connection whatsoever.
So, this bug should be extremely easy for Roku to instantly reproduce in this configuration and then that may also shed light on why it is also failing on the digital side.
Update to user11 post:
This appears to be a bug in the Roku Media Player (Version 4.2, build 1657)
The described problem only appears when Roku Media Player is placed in Display format (List) in Settings and then the Roku Media Player is exited and relaunched. It will continue to fail on every Roku Media Player launch while in this setting.
Both settings (Short rows) and (Long rows) work and correctly fill the screen both before and after using the (List) setting without resetting the Roku unit and without exiting the Roku Media Player.
I'd have to check the build of RMP I'm using, but I use the List view and have never seen this. I'm leaning more to it being an issue on the Express+, which I don't have. But in my Ultras, Premiere and TVs it's never happened.