It's not every day that we see both an adhesive and cohesive joint failure at the same location:
Improper joint design, poor material mixing, incorrect material selection, sub-par preparation; all leading causes to premature sealant failure. The example shown below is a very uncommon example of sealant failure. The main failure on this joint was a adhesive failure, meaning the sealant lost adhesive to the substrate. But in one lone area, there was a cohesion failure, which is highly unlikely to occur. Generally, an adhesion failure will continue throughout an entire joint due to improper preparation and installation. In this case it looks like one specific spot was prepared correctly but the caulk was installed too thin. Regardless of the cause of failure, this building is certainly in need of 100% sealant replacement.