So i had my kartboy short shifter and bushings installed today in a ‘18 STI. The reverse lockout gets stuck when i pull it all the way up. It goes into reverse fine and when i push it back down, the lockout works. Anyone have any idea why it might be getting stuck?

Sounds like something is binding w/the cable.

Either take a look at it and fix it or just take it back to whoever did the work and have them fix it.