JCR-160 clock radio Clock running slow (by 3 users)

Jensen JCR160 digital clock running slow

Tried JCR160 with 120v to 220v convertor in India found the clock looses 5 secs for every min.

Tried replacing 110volt input transformer with different 230v input transformer found no change.

Tried rewinding the primary side of the original transformer without disturbing the secondary winding & the voltage output still no change.

Any solution available ?....