dash display draining battery?

hi guys ! got a strange one here got an intermittant problem on my renault scenic new shape 53 plate,after locking the vehicle now and again the dash will relight back up and drain the battery this is happening about twice a month,have taken it to be diagnosed but they could not find a fault !! we now have to take the 20 amp fuse out over night as suggested by the aa repair guy........any ideas ????????? cheers