After Effects Render Artifacts
I've been working on a project and rendering out several sequences combining animation, videos and still photos. I need to render them with alpha channels, as they usually overlay onto other footage. The renders have been fine up to around yesterday, and now every single one has this weird pixellation happening across the screen.

I'm not even sure if it's visible there, but it's like rows of pixels that pop in for just a frame or two, then disappear, but it happens consistently through the render.
I'm rendering with RGB+Alpha using Apple Pro Res 444. I've tried clearing my cache, going up to 16 and 32 bit, taking my sections out of precompositions. I don't know what else to try. I don't know why this is suddenly happening now, all of my other renders have been fine.
I really hope someone has a solution! I don't know what to do!
Thank you
