Which pass do you look at for Radix Sort stability?
Radix sort always uses the results of the previous pass, not the original array.  It does not attempt to store the original value of the array.  You can find a description of radix sort at Wikipedia or in standard algorithms textbooks, and you'll see that it has this property.

As Wikipedia describes, radix sort is stable if you sort the digits starting from least significant and moving on to most significant.