Question GPU Crashing/Screen Flickering Under Load

Mar 19, 2019
Recently built my own PC.
I tried overclocking it but I fear I went too extreme, like kept it at 1450 Hz when Base clock is only 1200 Hz. Now Graphics intense games like GTA V, and Assassin's Creed Syndicate will crash during playing. Sometimes it will simply freeze and crash to the desktop, sometimes it will freeze and stay frozen until I reset the PC. Sometimes it crashes without it being too hot, I have my fan curve set high. On top of that, strangely, games run in windowed mode have no screen flickering, but games that run in fullscreen flicker. Example: when switching to windowed mode in minecraft the screen stops flickering, when in fullscreen mode it flickers immediately.
Some relevant specs are
Motherboard: MSI B450 Tomahawk
CPU: AMD Ryzen 5 2600
GPU: AMD Radeon RX 580
PSU: Seasonic Focus+ Gold 850

I'm pretty much just gonna replace the GPU and maybe even upgrade the CPU while I'm at it, but if anyone knows how to fix this it would save me a lot of money and trouble.