I found an issue after converting a tree particle system (The Grove 3d). For i wanted to distribute the tree with a particle system i had to join the twigs and leafs with the trunk of the tree (blender can't handle nested particle systems as far as i know).
After joining the objects, solid viewport still shows everything correct, while rendered viewport in RPR just shows some weird artifacts of leafs and twigs.
However, when i switch the renderer to cycles or luxcore, rendered viewport gives me the correct output.
I drop an image below to illustrate this issue.