Redring Powerstream Ascari PSA12 electric boiler

Does anyone know anything about these?

you can view the manual here https://www.manualslib.com/download/1831508/Redring-Powerstream-Ascari-Psa-12.html

Customer has just bought the house and complains that at 4AM every morning this boiler wakes here up. She recorded the noise once and it sounds like a vacuum cleaner running to me. Not a normal noise i would expect from a near silent electric boiler. It is still doing this every morning even if the boiler is programmed to be "off"

Reading the manual I see it has an automatic frost protection function, I can't see that being the culprit at this time of year.

It also has a "Pump protection - once a day operation when the system is off" I suspect that is the culprit and wonder if it is pumping against a closed motorised valve hence why so noisy?

There is no setting for this in the parameters menu. So I wondered if anyone knows a way to disable it, or at the very least, shift the time so it does it say mid day, not in the early hours of the morning?

Made some progress. I think it is the Pump Protection function. the manual says "Pump Protection, once a day operation"

But the problem is, it turns out it is not doing this once a day, but in fact FOUR times per day, every 6 hours it runs for about 5 minutes.

You can shift the time buy turning the power on and choosing the time you turn the power on, then it does this exactly 6 hours after you turn the power on, then every 6 hours. If it only did it once, then you could at least shift it so it does it in the middle of the day, but because it is doing it every 6 hours, you can't stop it doing it some time in the night while you are trying to sleep.