I've recently purchased a 65" Q80R and I have a problem with fast motion in apps.
I have a YouView box from BT connected to my TV, which I mostly use to watch football in HD.
When I watch games on BT Sports or Sky channel via cable, everything is butter-smooth and a joy to watch. Initially, I had motion setting at auto but even after turning it off the games were perfectly enjoyable.
The problem is with most apps, both the ones built into the YouView box and the ones installed on the TV itself. Whenever I watch football on any of the following, with judder and blur reduction maxed out, slow and average-speed motion is good but fast-moving objects seem to appear in three or four places along their movement path at the same time (I guess you'd call that judder). The ball, players legs on close ups etc., it's horrible and makes games impossible to enjoy.
The problematic apps are:
BT Sport (on the TV)
BT TV (on the box)
YouTube (on the TV)
The problem doesn't stop at football, any fast-moving objects behave that way, which I noticed when watchin Horrible Histories movie on Amazon Video app (both the box version and the TV version).
Surprisingly, games look great on BBC iPlayer app (box and TV).
My first thought was that maybe iPlayer streamed at 50fps while all the other apps did at 25fps, but I don't think that's the case. I believe BT Sport at the very least serves content at 50fps, although I wouldn't put my life on it. I'd also expect Amazon Video to stream at 50fps.
I tried turning Game Mode on for apps on the box and control motion from there, but it made no difference.
I'll be grateful for any hints.