I have not seen this, but I would like to look at network traces taken on the MWG box that show the connection to the ElektroDok AND to the support.conon.de web server.
Next time I will do my homework before posting in a public place. :-(
Looks like we do have an issue with our upstream proxy (hosted by our provider) and/or Canon itself.
If we bypass MWG and use the aforementioned proxy directly, the traces show the same results.
We'll have to investigate in another direction.