You have it, you have it? So there's no hope for my houses? Please tell me a patch will fix this.

I don't know anything about the patch, other than they never say exactly what they are going to do and have never said they will fix the lag. They have been this way for years because they know they can't fix the memory load problem. Lag is here to stay. As for the house thing.. I am just letting you know what I did. I always save before a big purchase like that and create a new save afterward in case something like this happens and I need to go back and try again later on.
I quit and loaded the game about 20 times or so and the racks never worked, so I decided to try and load the save before I bought the house and purchase it again and see and it took a about 5 times before I got one where the racks and shield mounts worked. They have been working ever since and that's a bunch of times into the house since then and they keep working.
So my limited test tells me, if they are broke with your save, they stay broke.