Speed Ramping (using Time Remap Speed) in Premiere Pro 14.2 doesn't work

There's extremely choppy playback, and the speed ramp doesn't work. It skips frames and won't show me the effect happening in real time. I have the playback quality down to 1/4 and still nothing. My machine has worked fine for years. I've looked at other threads; this issue has not been resolved. Can anyone help? This has happened on the macbook I've listed below and a far more powerful machine I use for work. This issue hasn't been fixed with the new Premiere update. 

I'm using mac OS Catalina 10.15.4 on a late 2013 macbook.

Processor: 2.6 GHz Quad-Core Intel Core i7

RAM: 16 GB 1600 MHz DDR3

Graphics: NVIDIA GeForce GT 750M 2 GB