With the thousands and thousands of WordPress plugins out there, both free and premium alike, it is very common to come across a plugin that causes more problems than it solves upon activation. These problems could include
- jQuery Conflicts
- Broken Layouts
- Conflicting Style Sheets
- Extraneous Resources that Increase Load Times
- Poor Theme Integration
- And More
and could be caused by either your theme or plugin.
Nearly always, these kind of problems are a result of poor or improper coding, by either the theme or plugin developer.
As an experienced coder who has answered way more than necessary support questions dealing with the problems listed above, I assure you I always try as hard as I can to adhere to the best coding practices as to eliminate as many potential conflicts as possible.