@Sasha T may I ask you if you are using multiple displays in your configuration? I'm not in my studio right now and I'll try once I will be, in the mean time I'm trying to understand what could be the cause of this issue. Would you like to help me doing some debugging?
I found a post that talked about some VSTs that uses GPU acceleration crashes Reaper due to a multi-displays setup with an nVidia card, especially with a 3 displays setup, I have 3 displays connected to my card.
That post says that if you run the plugin on a different monitor different from the primary one the bug appears. I did all my tests by running Mir Pro 3D GUI on a secondary monitor and the plugin in Reaper on the primary one. It seems a stupid thing but I must consider everything.
That post also states that Nahimic service seems to be the cause of the problem. I don't think I have that service but I must look into to be sure.
Thank you.