There seems to be a problem in \setuphead, it produces a spurious else from the alternative=middle. 

In the reference manual I see the possibilities: alternative = normal inmargin middle TEXT. Of these middle is the only one giving the else.

minimal example:

\setuphead[chapter][alternative=middle]
\starttext
\startchapter[title=TITLE]
\stopchapter
\stoptext

Is there a quick repair?

ConTeXt  ver: 2014.10.06 00:29 MKIV beta  fmt: 2014.10.6  int: english/english


Hans van der Meer