After upgraded into Unity 5.6 some of my Unity animations stopped working.
In Unity 5.6 the animations will not play properly even if I just put in the clean FBX. However, in older versions of Unity, such as 5.5 the animations are fine.
After a couple of hours of digging around, I noticed, there is a checkbox of “Resample Curves” in the import setting.
Just uncheck the box, the animations were fixed!!