PrintWidget ERROR 000590 after upgrade to arcgis/core 4.34

[SebastianKrings]

We were using the print widget just fine on arcgis/core 4.33.
After Upgrade to 4.34 we are facing this issue:

ERROR 000590: WebMap_as_JSON ist leer.\nWebkarte weist ungültige JSON auf.\nFehler beim Ausführen von (Export Web Map).

Saying the WebMap_as_JSON would be empty.

In the frontend it only shows this ugly error:

The Network Tab of DevTools give some more Info:

Dunno if this of interest but Print_de.json looks like:

Units_de.json:

GPServer:

Except to change to WebComponent instead of Widget I have no clue what to do.