Ya I noticed this error once. Never happened to me again. Let me see

<code>require_tree .</code> dose add all the JS in javascript folder to application.js recursively.
But some case if you want to avoid particular file from add to application.js or if you want to keep an order in adding plugins js, for example <code>B.js</code> should be after <code>A.js</code>, you should not add <code>require_tree .</code>