Not sure if this is a good idea, but is it possible to record the radio when you're on it "for real"? Then you could listen back to the recording of you completely blocking and cringe. Cringe harder than you've ever cringed before. My theory being that if you can create a situation where all your fears of blocking come true, and then re-live that situation over and over again through a recording, you'll be less likely to block because you've already gone through the worst case scenario so there's no more anxiety about the unknown that could cause you to block again... Just spit balling here, it might be worth a shot.