Change Instrument tool not properly working for transposing instruments
If you add a further trasposition on a trasposing instrument staff you experience a wrong (add up) of the trasposition interval on the latter instrument.
From this situation (Clarinet A [up a minor third]+ Piano):
You may change the upper staff Transposing Instrument into Clarinet Bb [up a major second] using the Change instrument tool from the Text palette, but you get this. This is obviously wrong:
say, the latter trasposition is somehow a sum of both ones [up a minor third]+[up a major second]
You can reset to the correct one by setting again the main key signature (here is G major) from bar 4 on: