airbrush backflow problem?

I have having a problem with my airbrush the past few times I have used it. Unless I have it nearly "wide open" for paint flow, it is instead back flowing and blowing air down into the paint jar. My airbrush is a bottom feed internal mix single action made by Thayer& Chandler for Promodeler. It most closely resembles the T&C Vega model 600(essentially identical). Until recently I never had this problem. On close examination, the needle tip is slightly bent and the nozzle slightly split at the tip. Is this the most likely source of the problem I am having? I have ordered replacement parts so replacement is not an obstacle.