Error: Transportnode: no next node from this transport

Hello all,

I hope you can help me. I had modeled my simulation model and put all processes together. Basically everything works. Robot takes the parts from the belt and inserts them, meanwhile he fetches the next part with the double gripper for direct deposit. Then the finished product is taken out, the new “raw” product is inserted and the finished product is placed on the next belt. However, after the robot has inserted the products into all the fixtures for the first time, the error “TransportNode Error: The transport solution does not have a next node from this transport node” occurs.
“TransportNode error: product not handled plane transport exit”. And this for all three devices (transport nodes). Below in the picture the error but unfortunately in German.
I unfortunately do not get the error when modeling the processes is also a transport input and output set, according to the program, the two points are also processed. Due to this error, the first conveyor belt then simply continues to run and the parts do not stop, so the robot can no longer grab them (picture).