>> How?  In attach_frame, the buffer where the positions came from is not
 >> known.
 >
 > It looks like the callers already take care of that?  Or did you find
 > a case where this is not happening?

How would you then explain the assertion failure I reported initially?

 >> Anyway, I passed an extra boolean to attach_marker to fix that
 >> and now I get a similar assertion violation in temp_set_point_both.
 >> This is a can of worms :-(
 >
 > Sorry, I guess you lost me: what did you try to fix and how?

I applied the attached patch.

martin