Buffalo, was it NPC? (Negative Peak Compression) if so, i don't think you want it. from what i heard it causes distortion even when adjusting modulation with NPC enabled.
if it were me, i would take/ship it to someone who is familiar with these newer, menu driven service adjustment radios. Michal from Scott's Radios LLC comes to mind. he has a ton of video on youtube.
seems out of the box the AT-5555n II's under-modulate AM, with too high a dead key at max power. they also severely over-modulate SSB. dunno about FM.
if anyone is considering this radio, i wouldn't suggest purchasing without a proper alignment. these are not good out of the box IMO.