Video Lags & Flickers Green Frames after Rendering?

Basically what the title says....
I've looked everywhere and it's so damn hard to find anything because of those who use green screening with AE.
Anyways... My issue is that I just put 8 hours into AE working on a project that is currently rendered useless at this point.
Wasted 17gigs & about 3-4 hours of my life searching the internet for no answer...
I'm just trying to get this issue resolved without having to redo my work... because I probably wont.

Basically. while rendering the video I noticed the preview was flickering green frames... Something it wasn't doing as I was editing the video itself & playing back through the preview.. but it seemed good after a few seconds passed by... all was good so I left it alone.
About an hour & a half goes by... video is finished rendering. Jokes..
I go to replay what I assumed would be a final product but wasn't anything beside 2 seconds of black screen, so green flickering upon the screen & the video being incredibly laggy.

I've had this issue for the longest time and nothing has seemed to help.

I've tried uninstalling, reinstalling... nothing.
Tried clearing ssd space... nothing.
Everything I try just doesn't work.
I've been on the hunt for this issue. I've seen other forums and their answers didn't help those who were asking & didn't help me either...
So I need to know how to fix this.. Was really looking forward to using AE for my channel again..
So please, I need someone to tell me that I'm doing something very slight so I can feel excited about using something I haven't touched since call of duty was a thing.