Hi
The difference with the R6S and the R6S+Pro is the Bare SATA support and the wifi. I have a couple of R6S and its warm when in use but not as you mentioned. Tried R6S+Pro for a TV Series marathon ok naman in an unairconditioned environment.
I share I do not use the bare SATA unless i really have to. I find the bare SATA nice to have, but plug /unplug may break the bare SATA connector that is board mounted, and as a klutz as I am, i broke a few back in the R200 Pro days.
So lesson learned--i get an enclosure and do it USB.
Just the same, my player rests on top of the console where nothing else is beside it. I run on my astone single bay 3.5" external enclosure (fanned), a 12 TB storage (USB 3.0).
for the "kurap", try to set your HDMI 1080p/24Hz and disable auto. disable 3D auto if your material isnt 3D. To be on the safe, scan your disks in a laptop baka may previously open file.
Units are for passive cooling (no fan) and dissipates the internal heat through its aluminum body.
If I may suggest - try playback from the USB and observe the chassis heat, I would think the Bare SATA support coupled with disk racked on the chassis gets the unit warm.