The FBX actually has value 0 at frame 17, the FBX contains a keyframe of value 1 just after frame 17, but at frame 17, the value is actually 0. So in the Animation Window, when the user clicks on frame 17, it's expected to see 0 on position.Z.
Issues are fixed by preventing the discarding of the keyframes if they have different values or different out tangents.