Immediately, if not sooner, have the memory battery on the circuit board inside replaced. The battery is soldered to the circuit board, and a competent engineer is needed. In UK they have become difficult to find, and the Becker factory do a good and fast service.
The usual reason for stored frequencies not being retained is a discharged battery. Discharged batteries, if not replaced quickly, leak electrolyte onto the circuit board causing damage needing circuit board replacement (cost about £150 at Becker).