One of those things that everyone knew back when a variety of hand saws were in every shop. For fine toothed blades, stone the sides of the teeth (lay saw flat on diamond or whetstone, make an equal number of strokes on each side of blade until kerf is .023 or a bit less). Another approach for saws with fewer. larger teeth is to place blade between two pieces of flat, very hard wood (ebony scrap or some of the ipe I keep finding and throwing out...scrap from decks...hate that stuff) and use a medium weight hammer to tap up and down the blade taking out a bit of set with each tap (uniform number of taps per inch of blade at uniform force).

The drawback to the first method is that the removal of set also causes some tooth geometry changes, but not an issue for the depth of cut we see in fret work. The drawback to the second method is that larger teeth on some very brittle blades may fracture if not well supported, although this is usually more of an issue with impulse-hardened teeth of Japanese pull saw teeth on cheaper tools.

If I were you, I would ask for a replacement. If like me, you opted to make your own fret cleaning and recutting blades (instead of buying SM's tool) from lengths of Exacto or Zonasaw blades, I would reduce the kerf using the first method. FWIW, the Zona 35-380 has a 16 tpi blade with .020 kerf that can be cut into short lengths and glued into the spine channel. At under $8, it's a bargain. Remove the blade from the spine with a vise, then cut to length with an abrasive cutoff wheel in a Dremel, etc.