Tefal GV8360 Steams for about 10mins and then stops steaming..anyone help?

I have the same issue with my gv8360.
* It works initially when it has been swithed off for a while, ie is cool when started.
* Then the steam button does not seem to activate or trigger steam generation. If left on for a while IT may somerimes start to function again, but only for a short period and then it stops again.
I have dimantled my steamer, cleaned IT out and checked for obvious faults.
- The tubes/hoses from the water tank and boiler are not clogged.
- The pump seems to work since it always starts when the steam booster button is pressed.
- Possible fault 1: the magnetic valve / actuator
- Possible fault 2: a temp sensor somewhere is hindering the steam actuation
- Possible fault 3: malfunctioning motherboard
I don't want to order spares before I am more certain about what the actual malfunction is caused by.
Anyone else with a similar problem?

Attila
September 2017