Aditya came across this in 2011 ([NTG-context] export kills hyphen symbol)[1] with the Fontin font. It wasn’t answered then. It is back if it ever left.
Here is an example:
If the \setupbackend statement is removed, or an invalid key is used, all is well. It fails with a valid key and any value for that key.\definefontfamily
[TestFont]
[rm]
[Antykwa Torunska Cond]
\setupbodyfont
[TestFont]
\setupbackend
[export=maybe]% or yes, or no, or ...
\setuppapersize
[A7]
\starttext
\input ward
\stoptext
--
Rik
[1] https://www.mail-archive.com/ntg-context@ntg.nl/msg58460.html