When the http or grpc address is already been used by the system (or by other extensions) an clear error message stating that a network cannot be bind on such network is shown in the logs.
However, for the debug address no error is shown. Only a info message saying "Shutting down sever".
It took me a while to backtrace the error.
{"level":"info","service":"wopiserver","transport":"http","addr":"localhost:9505","time":"2021-06-21T15:41:05+02:00","message":"starting server"}
{"level":"info","service":"wopiserver","transport":"debug","addr":"0.0.0.0:9109","time":"2021-06-21T15:41:05+02:00","message":"starting server"}
{"level":"info","service":"wopiserver","transport":"http","time":"2021-06-21T15:41:05+02:00","message":"Shutting down server"}