Intermittent hot water on Baxi 105e?

Hi,my boiler has developed a fault on DHW supply,when asked for hot water, system fires up runs for 30 seconds or so,LEDs light up then jump to 70 and boiler stops,then restarts after 15 seconds then does the same.Diaphragms have been changed in diverter valve assembly,spindles operate ok on DHW and CH valves.PCB has been changed recently and boiler cleaned and serviced. Model Baxi 105e,
any ideas or help most welcome,thanks