Just updated to 10.2 yesterday and a big mistake. When using Nix or Topaz half the time the file won't export out and once import back in the file is grayed out and can't be worked on. half the time I can't work on a photo in develop mode, can't copy my settings and the file won't export out.
I realize my experience will not fix your issues, but I just tried Silver Efex Pro with LrC V10.2 and it worked smooth and fast. My rig is Win 10, I7 8700K, 64GB Ram and GTX 1660 Super with Studio Driver. Catalog is on SSD. I tried it on a 8200 pixel Nikon D850 raw file.
Since I updated to V10.2 earlier this afternoon, I have searched for specific photos in my 180,000 image library, processed a few and all is working fine.
I'm using an iMac (2018 I believe) and I can at times edit one photo with everything and it works well but then I do another and everything fails and I have to close and restart the program. tried last time and got an error message that lightroom failed/unable to export the file for editing.