Ah, they joy of a packed filter . . . .
You may need to disassemble the filter to get the inside of the pleats and clean them out. A shop vac with a brush works great.
This is why it should be emptied frequently. 
I’m slightly concerned that the filter may require replacement. There has been a LOT of very fine dust from the CNC building up in that thing for quite a while (and very little emptying – especially the fine particulate filter). At a certain point, cleaning the pleats only goes so far. We can hope…
L
No idea if this is valid, but can one try to blow against the outside of the filters with
an air hose to clear them?
John2pt0