Bug confirmed. This is not corrected during the Partisan phase too, since if I rolled a 2, I got a Partisan in Persia which should not happen, because there are enough garrison points in Persia to prevent a partisan from appearing.
Russia hasn't conquered Persia yet. That will happen at the end of the turn (way after the Partisan phase). So right now in your game, Japan is the controlling major power for Persia. Since the Persian partisans are Red, they are fighting against Japan - which has zero garrison points in Persia.