Sorts will be removed from measure items in these cases:
Case 1 - You sort one measure item then apply a sort to a different measure item.
Case 2 - The sort on the measure item was associated with a particular level, and you remove that level from the view.
Case 3 - You sort a measure item then sort a level on the opposite axis.
See also Can Multiple Objects be Sorted in Views?
In this view, there is a sort on the Sales Units measure item.
Applying a sort to the Sales Amount measure item removes the sort that had been on the other measure item.
There is a sort on the Daily Sales Amount measure item for member C of the Product ABC Class level.
The Product ABC Class level is removed from the view; therefore, the sort is removed.
In this view, measure items are on the rows axis. There is a sort on one of the measure items.
Then a sort is applied to the level on columns, which removes the measure item sort.