It's broken. I just got the pack for christmas and I've done four reno gigs. Twice I've had the same thing happen that you described. Then one time I faced problems with locked doors and only once the gig went through without problems.
I had an idea but haven't tested it yet. It's to make sure the sims are on the same level when revealing the reno. I remember both times I had the problem my sim was standing on a foundation and the clients were standing on the ground. I don't know if this could be the cause.