I suspect the cats got in with the wood 5 inches from the entrance because they usually seem to enter at an acute angle to the doorway. So if you place an obstacle at one side of the doorway as well it makes it more difficult to get in. This is if you have an internal corridor turning immediately one way or the other. Place an object the opposite side to the way the corridor goes.
Re. the cat scarers. I am not convinced that any of those electronic scarers do not effect hogs, despite what some retailers claim. There is no way that they can legitimately/reliably test this. From my own experience, at one time I tried putting out a rodent scarer during the day time (which some claim don’t effect hogs). Once I forgot to remove it before the hogs arrived and I saw a hog pass by and visibly flinch as it did so. So I certainly wouldn’t use one.
The perspex arrangement I have described previously under this topic is still succcessfully keeping cats at bay, when many other methods which have apparently worked for others, have failed. Try combining the perspex arrangement with an obstacle one side of the entrance.