I'm having the exact same problem as this:
and similar to this:
I'm unable to find why my events listing page with the search form is having additional <p> and
I have tried with the 2014 theme preview and the events search page/form is fine, but I'm unable to find anything "strange" anywhere in my theme's code (Avenue) which could be causing the extra HTML code. I've also tried de-activating all plugins which didn't resolve the issue, as well as using different templates for my Events page. Nothing has worked.
Update - I have found the culprit! The Avenue theme shortcodes contains a filter function to format content (called "my_formatter"). I have commented out the code that adds this filter in shortcodes, and content no longer has additional <p> and
injected into it. Yay :)
Hope this solution might help somebody else.