Game Properties and Actions: Bug?

I control two shape keys with “sliders” that I made in the BGE. However, I can’t make them “overlay” (Both displayed at the same time), even when I set the influence to a vertex groups only affected by the respective shape key. I use game properties to set the shape key value.
Does anyone have an idea on how to solve this?
(This also occurs with object color actions. If I change the color, all shape keys reset, but not vice versa)

MultipleShapeKeysWithPropertiesInBGE.blend (550 KB)