The problem I'm having is a bug I can't find anything about on the internet. When I open up RCT3 these black shapes will flash on and off the screen very rapidly. They do from horizontally across the screen each one around an inch and a half wide around length the same between each one of these shapes. I would take a screenshot or video however if I open OBS to take a video the bars go away. That was until today anyway when whether I have OBS open or not the bug would happen anyway. If I try to take a screenshot it does not come up on the screenshot. 

I am wondering if anyone knows what this is or better how to fix it. I have RCT3 Platinum. It's the steam version and I have a Windows 10 PC

This sounds like a CSO issue rather than a bug in the game, if you've installed any new CSO's lately (CS, CFR's, or CTR's) try uninstalling the new ones and running the game again.

I honestly don't know because I don't have the same issue. The issue I had was with the disk. When I uninstalled the game after a serious glitch I went to install it again and it wouldn't install. So I bought a download on Ebay for it and that worked