I am not sure about the error reported on the offset, however, I can notice that there are 8 units selected while you attempt to number a 9th unit. Might it be related? Would you try by numbering the units from 1 to 8? That would be a good testing just to confirm whether it's related or not.
The problem is solved. When you build a stack, you either use only passive cables between stack members or use only active cables between stack members. No mixture of those cables together in stack ports. It was written in stack manuel but it was hard to detect.