R3D files do not show thumbnails when viewed in Media Browser. Video appears when hovering over a clip and scrubbing, but when the mouse is not hovering over the clip the thumbnails disappear. Identical issue to this post from May 2023. All R3D files behave this way regardless of camera source, resolution, size etc.
This behavior has been observed on Premiere Pro 23.2.0, 23.6.0, and 24.0.0
Mac OS Ventura 13.5.2
Apple M1 Ultra
128 GB RAM
NAS Storage