Suddenly Slow Export Times, Very Low CPU and GPU Usage

I'm really hoping someone can help. Premiere was running like a champ, and now, all of a sudden, exports are taking much, much longer. What previously took 5-8 minutes is now taking > 1 hour. 

My specs: 

CPU Ryzen 9 3900X

RAM 64 gb

GPU GeForce RTX 2060

2 SSD drives. 

The weird thing is when it's encoding, the CPU never rises past 10% utilization and the GPU never rises above ~5% or so. I'm encording using h.264. 

I've changed every setting I could think of. Software instead of hardware encoding. Switched from performance to memory. I've tried using the media encoder instead of PP, and nothing I do affects this bottleneck. 

And again, this is a recent phenomenon. When I first started using PP on this machine this summer, it was tearing through encodes. Now it's crawling. 

Thank you in advance.