Intermittent passenger rear indicator not working

[motorhomer2018]

Morning all.

I have a "professional built" (not DIY) motorhome that is based on a 2018 2.0 ecoblue transit.

On several occasions when turning left, the indicator will flash quickly, upon checking the rear indicator is not flashing.

Swapping bulbs with the driver side the indicator still does not flash.

When using the central locking the indicator does not flash.

But after an hour or 2 the indicator starts working normally again,

This has happened several times.

Do you think it is a problem with the motorhome conversion (loose wire etc), or is there a problem with the BCM (I think that it what it is called)

Thanks you for any advice given