The first error is a wrong spelled name of the column of table "InitialInventory" in Assign Labels activity "get address, qty,slot". The column name is written in complete uppercase. The name of the column in the activity is spelled "Äddress". I have updated in your model already. I inserted a delay and let the subflows run with only one instance at a time. Then your are able to check the error messages. I think there is a mismatch or a missing painted slot attribute in assigned slots. Also I deactivated the second process at all.
I suggest your are eliminating the errors in a much smaller model with lesser stock inventory. If and when the logic works, you enhance the model in some smaller steps by adding racks, painted slots and inventory table content.modello-7corsiepercorso-1.fsm