PGC 4 has R[13]=0 already, so isn't subtitle off by default already? Are you playing in PowerDVD? If so, it always turns on subtitle so it's not reliable.

Why don't you trace it in debug to see if subtitle is really on when playing the movie? You can see all the register changes there.

If you add precommand R[13]=0 to each episode, subtitle will always turn off regardless of your selection in the Subtitle menu. The only way to turn it on is via remote.