Please see attached UE4_anim_interp_bug.fbx for a second example.
This works as expected in 4.7 and 4.8
I've got a couple different users reporting this now. I suspected animation compression to start with, but that may not be it because it only happens when you import into the Affected Engine Versions. If I upgrade a project with the assets from an Unaffected Engine Version, the animation looks fine.
The older engine version imported a timeline that went to 6 keys for the 5 key animation, the affected versions appear to truncate it to 5 keys in engine. I believe this was intentional for consistency with Maya/Max timelines. Either way, this odd behavior seems to be an unexpected consequence.
1. Import each of the attached fbx files (include animation)
2. Each animation should move the red cylinder into each of the green rings
3. Open the ue4_ani_precision animation
4. Scrub through the timeline
Result: Seems to hit only 3 locations between the beginning and end, none of which land in one of the green rings
Expected: Each frame places the red cylinder inside a green ring
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-29112 in the post.