It doesn't make sense, I suppose, to move a single attribute from Rows to Columns (leaving the rest of the dimension, and it's attributes, on Rows), but Analysis let's you attempt the operation, spends some time churning, and then reports a large number of invalid combinations, and an exception requiring a Restart of the workbook.
I suppose the same exception would occur if you tried to move an attribute from Columns to Rows.
Analysis should either prevent the movement of atttributes, or handle the errors if you try. Anything that causes an exception or requires a Restart should be trapped.