I'm a real estate investor and actually have seen this in one of my investment properties. Unfortunately, the only way my crew says this can be fixed is by redoing the floors. Supposedly,this is from it not being installed tightly enough. I thought there would be a way to add a little spacer or something in to make it hold together, but after talking to other people in the field, if a floor is not put down properly, the teeth that hold the pieces together break and the floor needs redone. So, if I were you I would just kick the pieces forward with the heel of your foot when you notice it's separated, and try to just deal with the inconvenience until you are ready to replace it. Most all of the boards will be able to be reused, just the ones where it comes apart the most should be replaced.
Also, I have the swiffer wet jet and the multi purpose solution that you can buy for it works awesome! They have a wood floor cleaner, but it will leave streaks, so only buy the multi purpose. No streaks, and no time spent making your own cleaners.