15.0 and 15.1 don't let me edit Blackmagic Raw footage for more than ~2 minutes without becoming unresponsive and requiring me to force quit.
I am using Blackmagic Raw 2.0 from Blackmagic and ProRes proxies from an external hard drive formatted for Mac, edited on PC using HFS+ from Paragon. Premiere 14.9 works just fine with this workflow but 15.0 and 15.1 break it.
I am so sorry for your negative experience. Since Blackmagic RAW is not a supported format for Premiere Pro, which third party plug in are you using? Is the plug-in supported for version 15.0 or 15.1? Please let us know after checking.