Import Skinned FBX Issue

I am trying to import a skinned FBX in to Roblox, but when I do, some of the bones are in the wrong place.

In blender my rig looks like:

When I upload in to roblox:

Notice how the feet are being positioned in to the kneecaps.

Additionally, the animations are not importing correctly either:


I am using standard blender export settings:

Additionally, when I import, in the preview window, the feet appear normally placed:

Has anyone experienced such an issue before? I am not quite sure how to debug this.
Any help would be appreciated.