Pilot will stay lit but will go out when unit is...

Question

The pilot light will start just fine and stay running. When heater is turned to low most of the time the unit will go out including the pilot. Have changed the regulator and have a new 5 gal gas bottle because seems the unit is getting no gas. Hooked up an old bathroom heater to line and workds great so tank and regulator seem to be in workin order.