Per the title, the PF is in a state that it's like playing roulette as to whether or not it'll work.
1) This is the most common. Groups will form with 3 members. As of this moment replacing that 4th person is also not possible which leads me to....
2) It is impossible (or at least not timely) to get any replacements in dungeons. I can sit queued for the entire 30+ minute dungeon run for a DPS and not get one.
3) Zoning into a dungeon that "Is not my instance". I am promptly ported out and enjoy the loading screen. Double my 'pleasure' double my 'fun'.
4) Often as a result of 3) the group just plain disbands automatically. I don't know if this is one person leaving and the group itself disintegrates as a result, but regardless it's impossible to get a replacement using the PF per 2) right now even if that were the case.
5) Anything I've missed because I'm sure this isn't exhaustive.
This housing patch has been a complete debacle from the ground up. I realize this is a "I don't always test my code, but when I do it's in production" meme moments but it's really not amusing for a service myself and others are paying for. This is plain broken and has been broken for weeks now.
As this is a feature used by all players from level 10 to CP 600, I would think as a company priorities might dictate this as slightly important. For lack of a better way to put it, fix this nonsense. It was, far more than less, working before this abysmal aberration known as the housing patch.