Thanks for reporting Werner.
Unfortunately I am still unable to reproduce the problem, so I can not yet search for a solution. Any extra information on how to reproduce it is welcom.
I created a new
project at Bitbucket to share the modified code of xournal more easily.
It also has a Issue-tracker. I already submitted a few issues/enhancement-requests including the problem that Groen and you are reporting.
Can you (and Groen) check if the issue indeed contains the correct information and see if you have more info that you can share regarding the issue? If all is well you should be able to add extra comments to the issue (if not please let me know).
Everybody is invited to report new problems or enhancement-request there also.