X2 on possibly turning the valves on too fast. I've several propane things (weed burner, fry burner, grill) that have 'safety' features where if you don't turn the valves on slowly, something in the line thinks you've a loose hose and mostly shuts off. Don't know why this doesn't completely shut off (if you've a major leak, why have even a little propane coming?), and it is what it irritatingly is. Also don't know when these started being installed to irritate people.
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