'99 Subaru Shift Release Button

The release button on the shift handle has started giving me trouble lately and it seems to be worsening. I can’t push it in and have to try several times before it releases and I can shift gears. I’ve only noticed it when starting the car and putting it in reverse. Any idea what’s going on and how expensive a repair it is?



1999 Subaru Legacy L sedan, 150K, automatic