Yes initialising is reverting back to factory presets. Several things to check.
Does it happen when there is no rhythm being played?
Do you have only 'part select - right one' switched on or are the cymbals coming from 'part select - right two'?
Next to those two buttons is one marked 'left' - is that switched on?
Does it happen with all the piano sound options?
Does it happen say with a clarinet or a vibraphone?
Enough to be going on with...