I am complete newbie to BMS so take this with a warning
Had a similar issue with Saitek rudder (pro flight ones) and could not get the toe brakes recognised no matter what I did so I ended up deleting the axismappig file (actually renamed it first just in case) and voila it all worked just as expected.
Then left toe brake on the general brake axis and right on the right the brake.
All worked fine then.
OldBadger