Too Many Disparate Pieces of Software (What Happens When One Fails or Goes Out of Business)

An assessment of an existing and successful system showed a lot of disparate pieces of software hooked together in various ways.  An inability to properly define and build effective QA environments for testing meant that some testing was not done and taken on faith that it worked or was tested in production (and fixed).  No API testing was completed so any failure of any piece of the solution had immediate repercussions throughout the product and had to be fixed on the fly.

Lessons Learned:  A proper environment and knowledge and testing of the APIs would have solved a lot of the issues that showed in production.