The stationary face is not centered to the shaft. Shaft radial movement can cause the seal faces to separate if the hard face is not wide enough. In some cases the stationary face was broken when the deflecting pump shaft contacted it. The stationary seal face has been installed backwards and you are running on a non lapped surface. Only one side of a hard face is usually lapped flat.
Many manufacturers do a poor job of identifying the un lapped face.
The seal was set screwed to a hardened shaft. Seal set screws are manufactured from corrosion resistant materials. They are, therefore, softer than conventional set screws and can vibrate loose. Many packing sleeves were hardened to resist packing wear. The wrong lubricant was used on the elastomer and it is chemically attacking the elastomer.