How can I prevent my satellite clock from gaining?

How can I prevent my satellite clock from gaining?
My Sony Cube clock radio is supposedly satellite controlled, but it is slowly gaining and it is now approximately 20 minutes fast. It’s a lot of hassle to reset the time - and date, for it to recognise spring and autumn hour changes - so I am looking for a way to prevent its constant gain. It replaces a similar model which had the same problem. Is there any model which would not have this problem?

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