If you have a group divisi change (e.g. from unis to 1/2) and play a clef on the first beat of the split measures, the clef will be drawn on both staves but it only applies to the top one. See attached excerpt from a viola part. The treble clef staff is only really active on the top stave, but drawn on the lower, but the notes are as if still in alto.
This bug has been reported previously.