Builders or anyone that might know what has caused this?

It is an easy fix, just recolor the columns. You don't have to change the colors, just click the column with color changer thing, I forget what it is called. I believe you have to also choose the color when the little box of color choices appear. Once you do that the column with automatically revert to the correct size. But yes it is a bug, and they said they are working on it.

You could also build and delete a piece of fence or walls. That way you don’t have to recolour all of them.

@LaBlue0314 and QueenMercy thank you for letting me know.

I thought changing the wall height to the highest wall and then back again was the fix. What does changing the color have to do with the height? weird

You can also raise the foundation then undo it.

Columns are a problem in the most recent patch, before i'd have no problem with them, but now they just stick out everywhere, even putting them inside the house, the top part of the column is causing a texture issue with the second floors floor, flickering away. so a recoloring would solve this? hmm, i'll give it a try.