GPU Acceleration Slower

Been using 2017 1.2 and the performance has been very problematic since the 2017 release. Even using 1280x720 ProRes proxy files and with the Global FX bypass activated still results in playback stutter at times. I've experienced this on multiple mac systems running Sierra, including the 2015 TOL 5k iMac. Have tried Metal, Open CL, etc. It seems to get worse as the program is running longer (memory leak?). Often relaunching the program will result in better perf, but for a short time only.

So today, I turned off the GPU acceleration (switched to software only mode) on my late 2013 iMac and the performance was instantly better and with noticeable less lag. Is there something going on the graphics stack on the Mac? What's going on with Premiere?