You could try forcing the limits of the foot translations to zero. That should cure the foot from coming away from the shin, but I don't know if it will have any side effects in the Walk Designer. The text of such a pose is attached above.

The pose should be applied before the figure is brought into the Walk Designer.

[edit] The pose assumes that standard actor names were used for the feet.

@Miss Nancy

Quote - this is not good, if somebody is selling an unwelded set of props as a figure IMVHO.

Just because it does not have IK chains, does not mean it isn't a figure.