Parallels RAS Web Client stops working when policy option Always ask for credentials when starting

Dear sir/miss,

We're experiencing issues with the Parallels RAS Web Client. Whenever we apply the option "Always ask for credentials when starting applications" in the policy the web client (HTML5 version in the browser) just stops working.

When you double click on a session it tries to start the session and asks for a password. After the system asked you for a password and enter it all you see is a circle spinning around saying that the application is loading. You can basically wait forever (I've let it wait 1 hour) but the application doesn't load. Whenever we turn this option off, the web client works fine. I've tried this using the latest versions of Microsoft Edge, Google Chrome and Mozilla Firefox on 2 systems and none of them work. The official Parallels RAS Client (on both Microsoft Windows and IGEL Thin Clients) itself is not affected.

The issue is really located somewhere in either the Parallels RAS Secure Gateway or Parallels RAS itself, as I've monitored and logged my firewall and whenever this option is enabled and the session is started on the web client, there's no hits (or related traffic) on the firewall either, which there normally is when using the web client without this option.

Running Version 19.4.0 (build 24966) Sercurity Patch version 1, which is the latest as far as I know.