Problem with GuidedMu when MU has a fixed MU on it

Hello,

I use a guided transport system with a GuidedMU on it. 

This MU (WT-2) is getting loaded with another MU (Can) which gets fixed on it by a fixer.

After the WT-2 is lowered again it should actually get moved by TransportGuided system. But it is just shaking a bit, moving barely. After I delete the Can which is fixed on it, the WT-2 starts moving immediately. 

The WT-2 has a GuidedMU (Script) on it and the property "IsFixed" is true when the WT is lifted and false again after it's lowered and should move.

Sometimes it's working though the WT-2 gets moved normal with the Can fixed on it but somestimes not.

I'm not sure where the issue is and try to understand why it is not working properly.

Thank you in advance.

Andreas