Ahhh yeah I definitely didn't think the red doors would be one-way. I guess the problem was that the rest of the game all of the doors follow the same rule of 1 specific weapon = open 1 specific door color, so I never even considered that. A map *might* help if it has some sort of clear indicators there, but I think not putting the one-way lock on the door itself would be even better.
Instead of a red door, it could be a regular white door, but behind a gate with a button you can see. You can't shoot the button to open it through the gate, but it would tell the player "hey if I find my way to that door from the other side, I could open that gate for sure, especially since I know it's a white door"
I'm sure there's other solutions, that solution in particular I just stole from Super Metroid, which also relies a lot of weapon-specific colored doors like your game.
I look forward to the post-mortem!