Is it the room with the giant hand in it? Because I have the glyph from this one, but I'm still stuck with one glyph missing. There was another super rare room, a circular one with a big pillar in the middle, but I also have this one.It was never bugged, it's just a room that doesn't spawn very often. Some people have had better luck by going offline to find that glyph.
You can also save scum, create a save right before you get into the portal to B2, the biome gets generated anew when you go through the portal.
I did the save scum everytime I went to look for that last glyph ^^ I'm getting desperate lol