2013 Import Prius all electrics just turn off when parked

I'm asking for someone else.
They have a 2013 Prius C - it's an import car.
Well looked after and serviced and has run reliably for a 2 years with no problems.
Recently, the car when parked will JUST turn off.

Park the car over night.
Come back in the morning... and it just won't turn on.

Pressing the key just won't respond.
You have to use the manual key to get in.
Then... he says he has to open the car door and bang close the door with great force... then the car will turn on all of a sudden.

I've suggested to him that the key fob battery simply needs changing.
He says it's been replaced recently - in the last 12 months with good quality batteries (he says). He has 2 keys, both have the problem.

Shutting the door with great force makes no sense at all to me
I still think it's the key fob. I think he should try new batteries before doing anything else?

Toyota dealers won't touch because it's an import.

Any ideas?

Thanks.

 

Thanks for the replies guys.
I'll pass on the messages to the owner.

Surely if a loose connection, then car should suddenly come to a stop randomly?

ALSO if no luck self diagnosing... Where could the car be taken? A general mechanic or someone specialising in electrics for cars? (Wasn't sure if this existed)

The car is in North London. Just thought I would mention incase anyone could recommend somewhere nearby.

 

Just saw an old question I asked.
Problem got solved.
It turned out that there was a wire loose near the battery.

@sam spade 2 - you were right. The advice was really helpful.

>> And the obvious answer for "where to take it" is a Toyota dealer.
As mentioned in the post, they said that because it was an import, they didn't want to touch.