Stacker Crane - Single Pallet Error

I use process nodes with a Stacker Crane - Single Pallet to transport products. The first four products can be transported normally, but when the “transport out” of the fifth product begins, the following error is output:
File “Stacker Crane - Single Pallet::PMCrane”, line 42, in OnRun
File “Stacker Crane - Single Pallet::PMCrane”, line 579, in execute_next_action
File “Stacker Crane - Single Pallet::PMCrane”, line 70, in execute_pick
Exception: (‘Stacker Crane - Single Pallet #5’, ‘ERROR - Transport Node not found for pick’)

Does anyone know why this is?