The following code, a slight addition to test suite descriptions/labels-003.tex, when using ConTeXt from 20150904 and earlier works properly. Between that release and 20151004 something changed, and it fails with the labels shifted to reflect the temporarily narrowed text.

\definelabel[MyLabel][way=bytext,text=OEPS]

\starttext
    \setuplabel[MyLabel][alternative=intext]
    \MyLabel[labelname1] This is some text after \in[labelname1].
    \blank
    \MyLabel[labelname2] This is some text after \in[labelname2].
    \blank
    \setuplabel[MyLabel][alternative=inleft]
    \MyLabel[labelname1] This is some text after \in[labelname1].
    \blank
    \MyLabel[labelname2] This is some text after \in[labelname2].
    \blank
    \setuplabel[MyLabel][alternative=inright]
    \MyLabel[labelname1] This is some text after \in[labelname1].
    \blank
    \MyLabel[labelname2] This is some text after \in[labelname2].
    \blank
    \startnarrower
    \MyLabel[labelname1] This is some text after \in[labelname1].
    \blank
    \MyLabel[labelname2] This is some text after \in[labelname2].
    \stopnarrower
\stoptext

Oeps indeed!
--
Rik