I have had no problems with this. I have two living in my house right now. You have to make sure to do three things:
1. Make sure the undead part of him/her/it does not burn in the sun.
2. Make sure the potion has time to work.
3. Make sure your system is not glitchy. I have had sheep appear on a roof top, a suit of armor vanish, and wood turn to dirt. Sometimes our systems are glitch y from a bad connection. Trap the vile creature and then log out if you cant get it to work. Sometimes this reloads the code and you may find that you get a better result.
Remember, having a villager(s) live in your home is a big consideration. Zombies, and undeads will ignore you and do whatever they can to get in. Think of everything, even carpet, and don't forget that villagers can open wood doors. I installed button activated iron doors.