The issue with the trans is called the Park Pawl. It is unlikely that it is a cable issue if you can hear the pawl ratcheting. The trans will need repair to resolve a pawl issue. You said it went in with the issue? Your mechanic would have had an easy time of it while the engine and trans were out.

You can show that it has nothing to do with the converter by turning the engine off and seeing if it will roll in park. There is a SMALL amount of adjustment in the shifter cable at the trans lever but again, if it's clicking in the trans, I don't think a cable adjustment is going to cure it.