Hopefully, you can post the video. Even if you do, can you provide a little more information about your swing, your swing thoughts and what you've done?
Is it just off the tee you are experiencing this?
Have you tried changing your ball position? If so, what were the results?
How did you try to fix the issue that led to blocks and slices?
Do you take a divot with your irons? If so, what does it look like (direction, deeper on one-side, etc.) and is it properly in front of the ball?
What is your swing thought re: transferring your weight? Where is your weight (at address, top of back-swing, impact) and what part of your feet do you feel the weight (toe, heel, instep, outer) at each of these positions?
There are many pros who straighten one or both knees at impact (Furyk and Bubba being notable exceptions), so I'm not convinced that is your problem. However, if your pro is telling you your hands are faster than your body, combined with your weight transfer issue and, frankly, your experience, would lead me to guess that you are just really "armsy" with your swing instead of properly using the trunk of your body to generate your power. Spine angle could be an issue, too. I hope we get to see your video and let the pro instructors (not me) give you feedback.