Commonly caused by a time out when filling, draining or heating.
Low water pressure, slow flow rate, cold water inlet valves stick
when no-one is looking (but they never do it when you are there)
auto siphoning will also cause problem.
5p coin in outlet spigot of pump or in the drain hose itself, is common.
disconnect sump hose from tank and get rid of floating ball and its seating (they stick).
Check wiring to element and ntc is sound, check where the wiring
passes through air chamber, I’ve had internal breaks in that area
with little/no external sign.
Check alignment of door hook with interlock, quite often the door gets
bent downward, gently bend back up.
Remove door outer frame, insert substantial screwdriver or other suitable tool into rear of hinge and bend hinge slighty so that door moves a few
mm to the right.
Hope some of that helps