I managed to sync the data with
ftp.halifax.rwth-aachen.de correctly.
Despite my system did it's job correctly in this configuration over the years, somehow the rsync did not work properly anymore.
With some fundamental changes it is working again.
Thank you for your patience and all the questions arising.
As I have no control over the data on halifax, and donations are as rare as christmas, your questions gave me the feeling that the work I am doing here is still appreciated.
Data is uploading now and hopefully available in full size (~700GB) in a couple of days
AardFeeder