I've seen a few posts about this issue and wonder if anyone can offer advice. We bought a cottage that has a 9-year old Vokera Maxin 28e boiler controlled by a Danfoss 715 time switch. While it provides adequate hot water for kitchen, bathroom etc, we soon found it was locking out every 9th or 10th start. A service file showed this fault ran right back to the month after installation (May 2000) with more visits than Blackpool Tower and old bills for replacing: sensor electrode, start electrode, gas valve, o/heat stat, pump o/run stat, ignition unit, diaphragm. Last October a technician replaced the gas valve (again). Other repairs included : "remove air restrictors", "re-pressurized expansion vessel", "set htg gas rates", "adj. soft light", "cleaning fan, venturi, heat exchanger and burner". None of this has worked for long, if at all. Any thoughts?