wrong transposition for the sousaphone (treble clef)

Hi,

The sousaphone has a weird behaviour in terms of transposition.

I have a piece in Ab Major.
On the conductor, the sousaphone appears as treble clef with 2 flats, which is normal, it's a Bb instrument.
On its own part, is appears as a treble clef with no flats nor sharps. That is not normal.
When clicking "concert pitch" it appears as a bass clef with 2 flats. weird.

For the record, the Contrabass Tuba in Bb (treble clef) works perfectly.

Y.