Blending Animations between Third Person Project and Animation Starter Pack results in "dipping below floor level"

A number of users have reported that blending animations between Third Person Project and Animation Starter Pack results in a "dipping below floor level" between the two animations.

The cause of this is suspected that "the base animations IK was not constrained when exported" in one or both animation sets.

This is only a problem with the UE4_Mannequin Skeleton "Silver Guy" The previous "Blue Guy" works fine.

1. Open a new 4.8 Third Person Project
2. Add the 4.8 Version of the Animation Starter Pack to the project
3. Delete the Third Person "UE4_Mannequin_Skeleton" from ThirdPersonBP/Character/Mesh folder and replace it with the skeleton from the AnimStarterPack/UE4_Mannequin/Mesh folder
4. Create a new BlendSpace 1D
5. Blend between ThirdPersonIdle and Idle_Pistol
*Note that blending between the two animations results in the character "dipping" below ground level.
Expected: character should maintain Z position throughout blend