I've been using Boggs for around 40 yrs to sharpen/resharpen files and no complaints.
Some metals clog up a file more easily than others (pinning?). Depends on the cut and the user too,,how much pressure, etc. Softer the metal, the more they clog the teeth
Some of the steel castings used in the ML building trade are bad for this too.
If you use a specific file on Brass (or copper, silver, gold etc), keep it for that. Don't use it on steel also and back and forth. It'll clog up with steel much more when it's been used for a specific soft metal already.
Any but the rasps are easy to clean out with a brass cartridge case with the mouth hammered flat. But can be a pain to keep doing over and over again while working. But it's just the nature of the work.
Chalking the file helps,,sometimes.
I often dunk the file into a can plain water with a touch of dish soap in it while filing out a large project like a bbl or butt plate. That seems to keep the file clear and actually makes the file cut better as a sort of cutting lube.
Can be kind of messy to work with if you over do it. But you don't have to keep stopping to scarf clean the file teeth.