I have a New Englander pellet stove, 55-SHP22. I am having issues with an inconsistent flame. Flame goes from 6-8 inches down to nothing but glowing coals and back up to 6-8 inches again. It sometimes has a green flame as well. I tried the 6-4-1 , 5-4-1, and 4-6-1 settings, vacuumed the stove as instructed by the manual and still am having these issues. Anyone have any ideas on how to correct this situation. Thank you