The latest issue of Novum Testamentum has an article on Hebrews:
Guzmán, Ron, and Michael W. Martin. “Is Hebrews5:11–6:20 Really a Digression?” Novum Testamentum 57.3 (2015): 295–310.
Abstract from the Brill website:
"This study challenges the view that Heb 5:11-6:20 is a “digression”—a
view so widely held as to be a near consensus in scholarship today, and a
view that renders the controversial materials of chapter six tangential
to the central purposes of the speech. The study gives consideration to
ancient rhetorical theory concerning digressio, surveying the major
handbooks that discuss the figure. On the basis of this survey, the
study argues that only Heb 5:11-14 displays the essential
characteristics of digressio. Moreover, in its position and function,
this digressio actually points to the controversial materials of chapter
six as central to the speech’s cause."