patio heater pilot takes forever to stay lit?

My patio heater works like a champ when it's lit but lighting is another story.

I depress the valve,depress the ignitor button and all works well. The pilot lights. BUT,I have to keep depressing the valve for over ten min before the pilot will remain lit.

I thought this was maybe a thermo coupler problem(I'm not really sure if my heater has one or a piazo)and that it wasn't heating up fast enough on first lighting. BUT...

My bottle ran out and I immediatly changed to a full one while everything was still hot and STILL had to re-light the pilot by holding ten min.

I've checked the pilot gas tube for any webs,blockage,etc and double checked that all couplers are secure with no leakage.

HELP?