Back the adjuster all the way out and wrap 1 or 2 turns of Teflon plumbers tape around the threaded portion. Reinstall and done. The adjuster will still turn when needed but not as easily.
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Reviving because the solution turns out to be to replace the Promax brakes with TRP Sypres.
The Masi still has the Promax, but I had the same problem on a Cannondale Synapse with Promax brakes. Put on some Spyres, and the problem is gone. The Promax brakes jut out past the chainstay, but the Spyres sit nice and pretty over top of the tube. So they're a little bit lighter, they don't get hit by my shoe, and they actually do the job they were designed for. Will replace on the Masi too once funds become available.