I've fixed the 4th gear grind on an STi (and 1st gear grind on a WRX) by using one quart of Penzoil synchomesh in with 75w90 Valvoline NON-syn plain ol' tranny fluid (don't overfill it).

I reccomend getting the car back ASAP.
Escalate to SOA...and wait for resolution.
If that doesn't help, do my trick above.