 <p>I found another situation that could cause this to happen. I was converting a PHP function to a JS function and I had the following line:</p> <pre><code>ticks += "," . Math.floor(yyy * intMax); </code></pre> <p>Changing it to </p> <pre><code>ticks += "," + Math.floor(yyy * intMax); </code></pre> <p>solved the problem</p>