[itsme]

Setting a "Chord Highlight" colour makes it obvious what MobileSheets detects as a valid chord. 
Doing that shows that [H] is NOT detected as a valid chord. With source localization German [H] IS a valid chord, it is the chord that in source localization default is written as [B]
   
Transposing nevertheless works as intended:
Transposing from A to Bb, one semitone up, transposes A to B (Bb), B to H (B), H to C, C to Db
Now the transpose result 'H' of the second chord is displayed wrongly as B. Without transposing it was the third chord that was displayed wrongly
Note the 'B' as destination key in the transpose window: German spelling is used correctly