image with legend below (just in case)
1= low poly cube.
2= high poly cube (artifacts don't seen to appear in render for some reason, but do appear in preview).
3= low poly "blade".
4= high poly "blade".
orange= place that appear artifacts in preview.
blue= place that appear artifacts in both preview and render.
white= just shadows and reflexes.
os= windows 10 1909
cpu= ryzen 5 1600
gpu= rx 550
radeon software version= 20.4.1
RPR plugin version= 2.3.4
Thank you for request and for the scene. all information will be provided to the devs team. thank you
The problem still to exist in RPR 2.3.35 beta with Blender 2.83 from 27 april 2020.
Fixed in a future release