It seems that when I'm at 1 red heart or less, rather than just the door being open, it becomes a regular doorway (no more challenge room look to the doorway). While the doorway is at least open, is this some sort of visual bug?

@Niro Sure, I know that. What happens is that the entrance to the boss challenge room from the secret room always had the appearance of a bombed hole, but the error I mentioned is that the appearance of that hole simply changes to that of the entrance to the boss challenge room and also with some delay. That is to say that for a second the secret entrance looks normal but out of nowhere it becomes the entrance to the boss challenge. I don't know if I managed to explain myself well.

@Elpepemalo_ Actually that is not from my mod, it is how the game works.
From wiki:
"If a Secret Room is next to a Challenge Room, it can be entered by using a bomb in the Secret Room on the wall separating the two rooms. However, the entrance to the Secret Room from the Challenge Room closes itself, meaning Isaac cannot escape through the Secret Room entrance.
If Greed or Super Greed spawn in the secret room however, the wall leading to the challenge room will be barred up and cannot be bombed open. The metal bars do not disappear after they are defeated or if the player leaves the room, meaning they can only enter the challenge room the traditional way.
If Isaac bombs into either variation of Challenge Room through a Secret Room and leaves, the bombed entrance will close and must be bombed open again."

It has a bug, the secret room doors that are attached to the boss challenge room, that is, those that lead to the challenge room, look like they are boss challenge room doors instead of the secret room hole.

They were shit, so they added a new item pool to them, but also made them different to enter, i dont see an issue PeopleLikeStuff?

so nice ty

Never really understood that nerf tbh
Not like boss challenge rooms had consistently good enough rewards to make them only accessible at truly low health lol