Miscommunication or no communication - understand the application's requirements.

Software complexity - The complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development.

PROGRAMMING errors - programmers "can" make mistakes.

Changing requirements - A redesign, rescheduling of engineers, effects on other PROJECTS, ETC. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of keeping track of changes may result in errors.

Time pressures - scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines LOOM and the crunch comes, mistakes will be made.

Poorly documented code - it's tough to maintain and modify code that is badly written or poorly documented; the result is BUGS.

Software development tools - various tools often introduce their own bugs or are poorly documented, resulting in added bugs.

Miscommunication or no communication - understand the application's requirements.

Software complexity - The complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development.

Programming errors - programmers "can" make mistakes.

Changing requirements - A redesign, rescheduling of engineers, effects on other projects, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of keeping track of changes may result in errors.

Time pressures - scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.

Poorly documented code - it's tough to maintain and modify code that is badly written or poorly documented; the result is bugs.

Software development tools - various tools often introduce their own bugs or are poorly documented, resulting in added bugs.