Specs:
Mac Pro (2019)
Processor - 2.7 GHz 24-Core Intel Xeon W
Memory - 384 GB 2933 MHz DDR4
Graphics - AMD Radeon Pro Vega II 32 GB x2

As of receiving this new computer Premiere Pro 15.1 was the latest update.

My issue has two parts:
1) When exporting a h.264/5 the export is often very glitchy, cutting in random frames from other parts of the film or solid green/black frames.
2) When playing back the film, it often becomes very sticky, taking several seconds to catch up to when the playhead has moved or even crashing premiere when attempting to render.

Adobe support had two main suggestion both of which do not make a difference: to update my OS and make sure the h.264 encoding and decoding are switched off.

I discovered that both of these issues have a simple workaround:
1) For the export issue, exporting through Media Encoder and changing the renderer from GPU Acceleration (Metal) to GPU Acceleration (OpenCL).
2) For the playback issue, I changed the renderer in project settings from GPU Acceleration (Metal) to GPU Acceleration (OpenCL).

From this workaround it’s clear that Premiere wasn’t able to accelerate the export using Metal and there was likely a compatibility issue with my AMD Radeon Pro Vega II graphics cards . With the renderer on ‘Software Only’ everything works but is unbearably slow (not an acceptable solution). While the workaround wasn’t ideal, I was happy to call the problem solved.

One of my key issues with 15.1 was that rushes from the C300 often swapped their reds and blues. An annoyance that I found a solution for online but it was impractical for long running projects between multiple computers. 15.2 fixed this colour problem but introduced an issue where saving my project would result in an error so I quickly downgraded back to 15.1. When 15.4 released I updated and quickly found that both of my issues in 15.1 and 15.2 had been solved but OpenCL had been removed entirely as a renderer, making my workaround for the original rendering problem impossible. I’ve now retreated back to 15.1

Eventually Adobe support was able to help me figure out that by setting my export setting to ‘Render at Maximum Depth’, I would no longer get the export error. However, this same solution doesn’t work for rendering previews and playback in the program remains really bad, completely unusable.

I am now in a position where my very expensive computer is too good for Adobe who are not caught up to the specs of my Mac Pro 2019, (Avid, Davinci and Final Cut all list my specs as compatible). I am stuck at 15.1 and want to know when this issue will be resolved and my computer will be fully compatible with Premiere. Unless the AMD Radeon Pro Vega II becomes compatible with Premiere I will have to look at other editing software.

The idea being please can you catch up with Apple otherwise high spec Mac Pros are useless to the user, and Adobe is going to really lose momentum for film editors across the board.