Potterton Puma 100e flame stays on after DHW

[cmbcmbcmb]

Have just replaced automatic air vent on my Potterton Puma 100e combi boiler (which involved reducing the water pressure first using the pressure relief valve.)
Have refilled system, using filling loop.
But now, after using hot water, flame does not go out.
(So I turned on central heating for a while to get heat out of the boiler.)
Does anyone know what could be causing this?
Can I repair this myself, or do I need a gas engineer?
Is it possible that the expansion vessels need repressurising?

 

[Ihavenojob]

Look at the PCB,if the red LED stays on after running hot water its a sticking water flow switch usually caused by a leaking water flow valve.

 

[cmbcmbcmb]

OK, IHMJ.
I'm fairly sure the LED stayed on, but I'll check.
Thanks for your advice.