There is no flow limiting check valve in an opd valve. http://www.propane101.com/opdcylindervalves.htm
If your reg has a qcc fitting on it to connect to the tank (probably green female connector) they do have a flow limiter.. i would go to a standard POL connector (brass, left handed male threads)
another possibility.... your btu demand is exceding the vaporization rate of your tank and freezing up the propane.
By the time your getting everything shut off then relit your tank has had a chance to warm back up a bit and build up enough pressure for you to fire back up..