My son has a gaming computer and is having some video issues. Some games play fine without any issue (Call of Duty), but when he plays games via the xbox app the screen refreshes. For example it will have a bar that comes down the screen during game play (best way I can describe it). Is this a video card issue, memory or something else? His computer specs are below.

AMD Ryzen 7 7700X
32GB Memory
NVIDIA GeForce RTX 4070 Ti 12 GB

I am sure there may be questions I haven't answered, so please ask. Thanks in advance for any advice.

Sounds like xbox app issue or a gaming overlay from the Nvidia app. Can you show a picture of the bar? Is it just blank or does it have details in it like fps?

Could be a framerate issue. The GPU could be pushing frames at a different rate than the monitor refresh rate. In some games this causes problems with screen tearing.

I would start with trying the things in this video: