Hi @iansoon, thanks for all the information you provide, sorry I wish that we had already solved it for you! I extensively surveyed the dossier. Behind the scenes we conducted extensive tests and, like you said, the network operator KPN NetwerkNL was not able to resolve the issue. With the present information, we highly suspect that there is something wrong with the installation of the equipment. Therefore, Guidion should be able to solve this for you. As already more days have passed than I've liked I immediately tried to arrange an earlier appointment for you with Guidion. Unfortunately, they are really busy at the moment and were unable to help me out. Thus, I recommend you to keep an eye on the ‘wijzig afspraak’ button of the Guidion link you received. If an earlier possibility arises, the link will allow you to reserve it.
I have high hopes that Guidion will be able to help you out, the solution will soon knock on your door!