Welcome in H.C.M.
I have gone through your query regarding persistant coughingup scabs, phlegm from nose even after operation for sinusitis
twice about 2yrs and 10 years back respectively.
After considering your symptoms and co-relating it with possible etiopathology for sinusitis in your case is most likely allergic and that has progress to pansinusitis and ultimately osteomeatal complex get blocked. Your operation had cleared the passage but the allergic features will always appear from time to time as there is no permanent remedy for allergy
Here I would like to tell you that you use any steroidal nasal spray
for atleast 6 weaks upto 6 months to get excillent results and to avoid further complications.