Question about Sony Cmt-Sbt20b

I do not have this, it runs perfectly. In the operating instructions page 15DE it says:
When you select the function "DAB" for the first time after purchasing the unit, the automatic DAB search starts automatically and generates a list of available services. During the automatic DAB search, the search progress is displayed as a percentage. Do not press any button on the main unit or on the remote control during the automatic DAB search. Otherwise, the search will be interrupted and the service list may not be created correctly.
The search may have been interrupted and because the list was not created correctly, it will start again and may be interrupted again.
You could try to do a manual search according to page 16DE. If it does not stop after this, there may be a defect.