"Impossible Notes" that are perfectly possible may NOT be played back

I am currently writing a piece in which the tuba part uses Pedal A (A0). This led me to notice that even when I changed the range in the Staff/Part properties menu (bottom note in both ranges is now B-1), I couldn't get the playback to go any lower than E1. As a tubist myself I cannot fathom why this is the case; BBb and CC tubas are fully capable of pedal notes far below A0, yes, but I can't even get Eb1 in playback? Any five valved tuba (professional standard, pretty much, some have even more), is capable of playing chromatically down far, far below the piano keyboard, let alone a note found in intermediate tuba music. I play this note in my warmups, man, come on. If there is a workaround I have not found, I'd love to know, but I checked a loooot of forums and no dice.