Webinterface not working after upgrading to traveler 8.5.3 Upgrade Pack 2

We had an issue with the traveler webinterface after upgrading to 8.5.3 Upgrade Pack 2.

The webinterface didn’t show any content:
Traveler webinterface without content

It is working when accessing one of the traveler servers directly, but not when using the external proxy URL.

During the setup procedure, some changes will be applied to the website configuration document.
But in our case not to all of them (we have different ones for internal and external access).

There is a new setting in the website configuration document, which seems to be essential for the webinterface to work properly.
Open the website document and go to the configuration tab:
Website configuration tab

At the bottom, add “TravelerAdmin” to this field:

Website config tab2

“tell http refresh” and it works…