Thanks for the quick response. It took a while to get screenshots from the unit that was out with the client. Meanwhile they managed to downgrade the unit from TRB2_R_00.07.00. to TRB2_R_00.02.06.1
With this downgrade we can now see the image from a connected camera, we still want to check it with more devices, but our preliminary conclusion is that the OpenVPN of connected devices does not work with TRB2_R_00.07.00. Of course, for future upgrades it is important for us to have these things under control.
(BTW: I can forward the screenshots if needed, I have 12 of them, but it would be faster if I could just email them to tech support)