Bounce rate and WP web design pro

We have made some changes to our website on the advice of a speed page pro and all of a sudden our bounce rate has dropped to almost 0. That may sound good but it is not and means something is wrong. Our developer has looked at many things, eg analytics code added twice, conflicting plugins etc but we cannot find why it has suddenly disappeared like it has. We need to figure out why. 0% bounce rate is not a good thing as far as Google is concerned. Please tell me why you think you should be awarded the job. No pitch, no job