I have had a problem downshifting from 5th to 4th on my 05 legacy gt wagon with 5 speed manual. Yes, I push in the clutch all the way, but for some reason on some occasions it just won't shift into 4th although I can brake and shift directly into third. I wrote to SOA about it, and they informed me that "Subarus are not designed be downshifted" I owned a WRX before that and on Outback before that and never had that problem!
Most times it will shift o.k., but with some resistance, the times it won't are probably about 10% of the time. It can happen at speeds of 80 or 45. Double declutching does not seem to help. I was hoping that after I put a few more miles onto the car things would improve. I now have 15,000 on it and it is no different than when new! I have not read of anyone having a similar problem, but would welcome advice from anyone who has. Since installing a Cobb Access port the problem occurs less frequently simply because the car has more torque and it is not necessary in most situations to downshift for extra acceleration. I still have the problem just the same when the traffic slows and then picks up as when I slow down I try to change down to the next lower gear so as to be ready to pick up speed again.