Without the model file there is not much I can do.
Can you upload your model?
I changed some things and then the error didn't occur again. I just thought it might be interesting for you to improve the programm, but unfortunately I didn't save the error version. Sorry!
It looks like you get a conflict. At the exact time when you change the entry sequence, one MU is passing by (as a result of the old sequence) and another is being admitted (new sequence). I think that as a result the software gets lost.
Maybe @MichaelJoos has a suggestion. The current mechanism is quite simple, but maybe we stress the boundaries too much. The alternative is to program a Pull-control.
I guess it also depends on the blocking or unblocking mode of the material flow control. If it is not blocking, I don't get an error message.
Moreover, I get an error message at 20:00:30 although all MU's only should be pulled out of the system. That's strange, isn't it? It's in the same model.
I can reproduce the problem, and I will look into it.
The problem occurs when you set a new exit list in the flow control 'Raus'. The old list had 5 items, but the new one has only 2. When you set the new list, the cyclic sequence is at position 3. Unfortunately the flow control did not check, if the new list is shorter than that.
I fixed that bug, but since you are using a Student License, you do not have access to hotfixes.
As a workaround, you could reset the current sequence position each time you assign a new exit list or entry list, although this would change the behavior of your model. On the other hand, keeping the old position is questionable anyway.
You can reset the current sequence position by temporarily changing the exit/entry behavior:
Raus.Ausgangsverhalten := "Reihum"; Raus.Ausgangsverhalten := "Zyklische Folge";