The problem with bi-fold doors is that only three of the four corners of each door are secured by hardware, and although the door must roll along a track, you have to pull outward to get the door rolling. This creates stress on the rolling guide and leaves the bottom inside corner of each door vulnerable to abuse and consequently getting out of alignment. Original article: https://www.reviewjournal.com/life/home-and-garden/bi-fold-doors-are-vulnerable-to-abuse-getting-out-of-alignment-2909622/
