Shimano Tiagra STI lever return issue

Hello, my STI (right hand side) doesn’t return fully after pressing the brakes. My local mechanic said it was just new and I just need to use it kore and it will eventually loosen, he said that it has something to do with the bushing rubbing and causing friction. My brakes callipers are unaffected tho, it releases when I release the lever. Has anyone experienced this on their STIs or have any insights. Thank you!