Somewhere in the debug printer, strings containing HTML encoding (such as the HTML encoding of User.Name@stackit.cloud -> User.name%40stackit.cloud) are interpreted literally as printf format values.
This leads to DBG output lines like this
DBG request to https://resource-manager.api.stackit.cloud/v2/projects?limit=50&member=User.Name%!s(MISSING)tackit.cloud&offset=0: GET HTTP/1.1