v18.0 won't cache frames, and won't let me edit or add new text layers

The green "cached frames" bar by the playhead continuously flashes as if it is constantly caching a single frame, even when not in playback. When I do playback, it won't cache frames, it just buffers the next frame in real time and then moves on, not allowing me to ever view my work in realtime. 

A side effect of this is when I try to add/edit text, as soon as i click anywhere in the viewport, it immediately exits the text layer as if it's trying to simultaniously playback (without actually playing a preivew).

It's just in this specific project too, i've tried migrating this project to a new one, in a new version of AE, but it still happens. I'm not using any footage, just photos and text layers. I've tried purging my cache several times too.