I’ve had a WD TV Live for almost 3 years and recently picked up the newer Streaming model before Christmas when WD had a $50 cashback promotion here in Australia.
Connecting it to a Samsung 60E8000 model plasma which does not have any sort of motion interpolation (Panasonic call their version Intelligent Frame Creation), I observed the exact same behaviour as Sanjuro.
It didn’t happen on all 23.976 frame rate MKV files but happened often enough to make it unuseable. I would actually describe it as dropping frames rather than stuttering.
It happened with 720p and 1080p files.
The same behaviour was observed from an NFS network share and from a locally attached USB drive.
It happened with autoframe rate on or off (with it off and HDMI output set to 1080p/24).
It happened all on firmware versions that were available at the time from 1.08.17 to 1.12.14.
It didn’t happen when output was set to 1080p/60.
As a final test, I remuxed an offending test file from MKV to M2TS using tsmuxer and it played perfectly.
And, of course, the original MKV file played perfectly on the older Live model.
I have since passed the Streaming player to a friend who needed a new player for his kids and set it to 1080p/60 as they don’t care about the pulldown introduced when going from 23.976 to 60.
Sanjuro, perhaps you could also test remuxing to M2TS and see if it plays okay?