Problem with loading assets in Publisher 4.3.0

Recently I upgraded to Publisher 4.3.0. After that I am no longer able to import assets from a finnished Auphonic production.

While accessing a fresh episode draft I get this error message popping up continuously:

rest_no_route: Es wurde keine Route gefunden, die mit der URL und der Request-Methode identisch ist.

I see existing production in the Auphonic menu but import of asset files and title metadata is not successful.

I tried to logout the Publisher from Auphonic and reconnect, without any change.

Update: I disabled the Auphonic integration, the error continues. The asset file menu and slug field are showing a wheel of death, without loading.

Similar behavior on a second podcast with similar Publisher version.

Update: Downgrade to 4.2.7 made the problem disappear for the moment.