Reduce Reed Sticking
A student came in for her lesson yesterday and she had the issue of multiple harmonicas having draw reeds that were stuck. I unbent one side of a coated paperclip and handed to her so she could massage the offending draw reed across its length and it quick unstuck. I observed her playing and noticed that the back of her harmonica tilted downwards, essentially allowing gravity to do its thing by allowing saliva to travel down the draw reed plate, over time building up around the reed and its slot, causing the reed to seize. If you also have issues with reeds sticking, look in a mirror (side profile) to see if you too are allowing the rear of the harmonica to droop. The goal is to have the harmonica horizontal or the face tilted downwards (which I recommend, from 15-45 degrees).