After Effects 2020 suddenly struggling to render preview properly - "laggy" rendering

Hello. I'm somewhat new to AE, so apologies if the answer to my question is obvious.

I'm running AE on a 2020 MacBook Pro: 2.4 GHz 8-Core Intel processor, 32GB of memory -- so it is not a CPU issue.

I've been able to create numerous projects seamlessly over the past months.

While in the midst of creating a recent, rather long project (with tons of external footage), I suddenly ran into an issue of my render queue being "laggy". Not laggy in the sense of my CPU having a difficult time rendering footage, but that the on-screen visual play-back has begun appearing glitchy. In playback speed, it is appearing in multiples of ~6-12 miliseconds at a time. 

I've already cleared my render queue, as well as adjusted some other quick fixes in my preferences menu -- such as previews (zoom quality, color management quality) and display preferences, but I am truly stumped here. Any idea what could be causing the issue?

Thanks.