Time Machine has a great reputation as being a solid and robust backup system that can be used in a number of ways, however, as with all systems, it does have a few quirks. For example, sometimes backup runs can get stuck and not continue the backup. In these instances, though one or two backups may work fine, the system will start pausing at the "Calculating Changes" stage and never complete additional backups.
If this has just started happening, try just waiting it out. When there are major changes to the filesystem, Time Machine will do a "… Read more