After I posted my question I did stumble over another user with the same problem:
I should note (in answer to questions made to him in that thread) that:
I did not use the sync beta software – my syncstore was created in the released 2.9 version,
and
For some reason, nothing happens when I choose the “Report Bug” function in DTOP. If this is supposed to generate an email, I should note that I do not use Apple Mail (PostBox is the default mail client on my system).