Layers disappear and flicker

Objects are turning black, disappearing, and flickering. I didn't make any edits or anything since I last worked on it (worked fine then) but when I opened my computer to the open file it started glitching. I exited out of the document without saving because I assumed my previous save from when it worked normally would save me. When I opened my save from before the glitch, it was still glitching, and it got even worse. My layers are mostly imported from Illustrator, but I didn't touch the file I had on there either. The layers in the project window also show up mostly all black when I look at their previews, although I am new at AE so unsure if this is common. I am working on a Mac and the program should be up to date. Any ideas on what could make individual art objects flicker or turn black?