To start, I’ve read everything I could find on how root motion should work, how to enable root motion, show → “Process Root Motion”, etc. And in fact, it does work… just not with Blender FBX. There, it 2/3rds works, which is the odd thing. (Other animations work fully.)
With root motion disabled, I see the proper red bone/path warning that root motion exists. This animation plays properly as-exported, along its root-motion path. When I enable root motion, the animation is properly locked in place, as expected. However, when I enable “Process Root Motion” … it processes a very tiny root motion, i.e., it slowly creeps along the path as if it’s scaled way down. This is the same whether I use the 7.4 binary exporter (with an “armature” root, with root motion keyed to the armature), or a “fixed” 6.1 ascii export, with a single root. I have attached the latter. (Note it needs a 100x scale on importing, which the 7.4 exporter does not, but this version is less ambiguous.)
Importing a similar animation from Maya LT seems to produce the expected result: proper red path, properly fixed in place, and proper process-root-motion.
I’m using 4.12.4 compiled for x64 with VS2015 Community, along with Blender 2.77a.
Hopefully I’m doing something obviously wrong.