I don’t know about clarinets and saxophones, but 10 cents off seems like a lot, especially with the kind of variations you you mentioned, for a melodica. I wouldn’t expect that with a new M-32C. How are you measuring, and how consistent are your readings? Are you using an electronic tuner, a tuning app or online tuner? I go through the process of getting initial readings several times, blowing at a moderate level comparable to what’s typical in my playing, after warming up the melodica. If I’m having trouble getting consistent readings, I blow each note hard several times before getting a reading — I’m doing this by ear. With experience it gets easier to get consistent readings. Also, I think it’s better not to try tuning until after getting a feel for the instrument and what kinds of sounds you’re getting in playing it normally, also getting a subjective impression about the extent to which it sounds in or out of tune.
For some reason, it’s harder for me to get consistent readings on a Suzuki than on a Yamaha. Actually, I think I know the reason, which is that the Suzuki’s reeds are less stable, which isn’t necessarily a negative.