I have this blocking issue. The word is just stuck. What I do is speak slowly or use extreme pronunciation. I have been doing this while teaching (yes, this PWS is a teacher). I think my students know that I have some issue with speech, but as long as I can convey the topic to them there is no issue. Also, try to read aloud as much as you can and try some tongue twisters. Sometimes, if nothing works, I just remain silent for 2 seconds and start again. People are usually understanding. We ourselves have set very high standards for our speech. I am sometimes tense in my lectures, but it has worked so far. I hope it continues to work. Good luck to you!!