Regulator may be fine.
Let me assume for a second that your tank and regulator are somewhere aft, and a hose leads into the boat and then to the Shipmate. Second assumption is that the hose has a low point below the level of the Shipmate (probably a foot or two). In such case, this 'oil' may have collected in the low point of the hose and the 1/2 psi of pressure isn't enough to blow past the oil, or perhaps only bubbles past the oil slowly with loss of pressure.
If such is the case, you may want to disconnect the hose from the stove, eliminate the low spot by lowering the end of the hose, and then blow the oil out of the line. The right way to do this is to also disconnect from the regulator and then blow it out using compressed air - got a bike pump? The wrong way is to blow it out using propane from the regulator, but of course you're smart enough not to try this (right??).