Oh Yes, that is the problem. A HEPA filter will restrict air flow and clog up very quickly! I use dust screens but the ones with wide spacing. Even those have to be cleaned 3 or 4 times a year or they will completely clog up too!
However the screens are easy to clean, just peel or brush the dust off the screen surface.
See screen in blower pic below.
Do I see yet a different configuration on that stove Don?