1. Inspect The Specified Position

WARNING: This page is about a different car, the 2013 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

If the stop light switch does not operate properly (or if it is not secured at the specified position), replace with a new part.
Specified position L:

2 mm (0.079 in)

Fig 1: Identifying Stop Light Switch Installation Position
Courtesy of SUBARU OF AMERICA, INC.
Measure the clearance between the threaded end of the stop light switch and the stopper.
CAUTION:
Be careful not to rotate the stop light switch.

Stop light switch clearance A:

0.3 mm (0.012 in)

Fig 2: Identifying Stop Light Switch Clearance
Courtesy of SUBARU OF AMERICA, INC.
Adjust the position of the stop light switch if the inspection result is not within the standard value.
CAUTION:
Be careful not to rotate the stop light switch.