Sims unable to enter the house

In my case the problem was not solved by entering build mode. I removed/replaced the door, removed/replaced the steps, tried setting the back door as the front door. While I was trying everything I possibly could think of to get my two sims ro enter the house the third sim came home from work and walked straight in without a problem. But yet when I told him to fix something to eat he could not get to the refrigerator. All of this happened without any cause. I had been playing the same house for weeks when all of a sudden all these routing problems.
I did move the entire family into a new home and there are no problems. But I do wonder what happened to cause my house to be unusable.