Light five flashing is supposed to be a fill valve fault, it could be intermittant valve failure but as it is an Indesit it could be almost anything else as well, pressure switch, water in base, blocked filters, control PCB etc.
hi, it will be the water heater shorting to earth,
the electronics will not recognise the readings it is getting from the faulty heater, and the nearest it can find in its memory is a valve fault, dont ask me why, but trust me, unplug machine, gain access to the heater & with a decent test meter you will find the tubular heater has failed