Can anyone figure out why this animation/bone jitters?

I have a mesh created in Fuse and rigged/animated with Mixamo. When my character moves using a walking or jogging animation, I can detect a small jitter in the animation or bone. It is more pronounced if I rotate the camera (in-game capture). I’m not certain I can detect the same jittering when I view the animation in Motionbuilder (Motionbuilder capture mesh / skeleton). I have no idea if the jitter exists when viewing the animation in the UE4 editor (editor capture). I think I have been staring at this animation too long to tell anymore.

The only thing my Google searches have found was some animation/bone jittering when a character is far away from the world origin, however I have set the world origin to the player location at the start of the game and it hasn’t fixed anything.

I would really appreciate any sets of eyes that can look at these captures and tell me where the jittering exists and where it doesn’t, or if there’s something I can look into changing in regards to the animation or skeleton or UE4 settings to fix it. I am using the (almost) default third person camera settings and I haven’t noticed these issues with the default character mesh/animations.

I posted this to r/unrealengine on Reddit and got a couple of responses that confirmed some of my suspicions, but no solutions. One response says that it is definitely an engine issue. My thoughts were that it might be an issue with the skeleton, so I made sure the base mesh+skeleton FBX included proper floor touch points in Motionbuilder, but that hasn’t helped.

I don’t see a jitter but a pop as the cycle is completed and starts over at frame 0. This is a typical problem in Motionbuilder where the cycle does not ease out and into the next frame as the cycle is ending at say frame 24 so can not interpolate to frame 0 as being pose to pose.

The result is not so much a pop but an effect of a hold occurring on the last frame back into the first frame instead of looking like a single and constant motion of running

Compared to say.

The difference between the two reference is yours the arm movement stops at the end of the cycle where in the slow motion video the arm is in a constant state of moving forwards and backwards.

The easy fix to get a consistent cycle is to plot on frame the full cycle and pull half the keys, once again as an example, 12 of the 24 frames so that the first frame starts at the last frame and smooth out the interpolation of the original ease in and out.