[lwrcase]

This is exactly the same thing I experience on my NUC7CJYH. Turning on any sort of info overlay on the screen stops the "stutter". It doesn't happen all the time, but I'm going to try and grab a debug log today when it does.
Looks like there was someone else with the same issue that solved it with some config changes to DRI/Mesa - https://forum.kodi.tv/showthread.php?tid=299115&page=7    

it looks like /etc/drirc is read-only on libreelec and i wasn't able to add the lines to the configuration. anyone know how to try this fix on /etc/drirc?   

Have you tried setting the i915_min_freq value to 750 as Fritsch mentioned in this post: https://forum.kodi.tv/showthread.php?tid...pid2722375 ?

Can you try before starting the movie, from a shell: 
echo 750 > /sys/kernel/debug/dri/0/i915_min_freq

Prior to increasing that i915_min_freq on my Apollo lake nucs, the fps would hover around ~56fps (as seen on the debug overlay) when I was using 60Hz fixed refresh rate.  This would result in skipped frames and stuttering when I was *not* using "Adjust display refresh rate" to On (when I was using automatic refresh rate matching of source material, things looked fine).  After increasing i915_min_freq to 750, the fps would stick solidly at 60fps and my 23.98 fps content would play smoothly on my LG oled TVs when not using automatic refresh rate matching (which I prefer to not use when I'm just flicking through videos).

Also when I increased the fixed refresh rate to 120Hz (which the LG 2017 oleds are capable of), the debug gui stays locked at 120fps and 23.98fps content also appears stutter free. 

 echoing 750 into i915_min_freq gives me a permission denied error.

i have also tried setting "Adjust display refresh rate" to "Always" without any improvement. Also "Sync playback to display" to "On" without any improvement.