A call to \switchtobodyfont introduces extra vertical spacing as can be seen in the example.
Is this intentional or is it something like a % missing somewhere in a macro?

Hans van der Meer

Sorry, flew accidentally to early away. Here the attached output.

\setuppapersize[A6][A6]
\setupbodyfont[lucidaot]
\starttext
First line.\crlf
\start
\switchtobodyfont[euler]
Font switch here.\crlf
\stop
Last line.
\hairline
First line.\crlf
\start
Font switch here.\crlf
\stop
Last line.
\stoptext