Hello Shuo,
First things first. You are making great progress! Congrats!
Next, let me show you the best way to debug. In our case the planar joint seems to be the issue. So let's first delete its connection to the rest of the assembly. So disconnect the line between Wheel/F2 and Planar Joint/F. Now update the model. You see that it does not error out. This is good! Because Now we just need to align Wheel/F2 and Planar Joint/F appropriately.
Wheel/F2 and Planar Joint/F need to be at the same 'Z' location. They can have some leeway in X and Y directions. Why is this? Because using a planar joint we are going to allow translation between X and Y. However ONLY revolute is allowed in Z. This means any discrepancy in Z position between Wheel/F2 and Planar Joint/F will result in an error. Let's take a look at this graphically to see if this is the issue. To do this, let's use the mechanics explorer.
ISO VIEW
FRONT VIEW
You can see that the frames are translating a little in the Z direction. This cannot happen since Z can only allow revolute motion.. You need to take a look at your translation blocks and figure out how to align Wheel/F2 and Planar Joint/F. You need to look at the various dimensions specified to get to this translation.
