If the gearbox warning hasnt come on, and you have an abarth it may well not be the brake switch.
The brake light switch is required for the correct operation of the gearbox as well as cruise control and traction. If you arent getting those errors it may well be something else.
When my brake switch failed cruise control wouldnt enable, and the brake lights were constantly on.
Have you tried backing up to a wall or something and seeing if your brake lights are working okay? If they are it may be a brake switch with an intermittent fault or something else all together.
If you have a code reader or diagnostic equipment its worth checking as it will log a DTC for the brake switch.