This meaning of the adjective dusana/gwgos seems to be confined to writers of late antiquity and the Byzantine age. See e.g. John Chrysostom, Ad eos qui scandalizati sunt 7.1, where this term occurs together with duspeiqh/s: a)ll’ e)peidh/ tine/s ei)si ph/linoi kai\ dusana/gwgoi kai\ duspeiqei\s kai\ au)to/sarkes; 'but because some are made of clay and hard to convince and disobedient and carnal'.
Prior to that it is chiefly a medical term, 'hard to bring up' (often in reference to mucus), and is frequently attested in that sense between the first century AD and the fourth, when John Chrysostom and other Church Fathers start to use it in an abstract sense.
The presence of the latter-day connotation in the Suda, however, is probably an accident -- because this entry (also in ps.-Zonaras) seems to be a variant of, or error for, an entry for a different adjective, dusa/gwgos ('hard to guide'). In Photius, Lexicon delta789, for instance, we find *dusa/gwgos: dusxerh/s, a)peiqh/s; 'hard to guide: hard to deal with, untrusting'. The same entry appears in one ms of Synagoge delta382, although the ms followed by Bachmann (202.11) and Cunningham has duspeiqh/s ('disobedient') in place of a)peiqh/s. See also Hesychius delta2507 (s.v. dusa/gwgos).