You need to discuss this with a workers compensation attorney. I will add that to your tags.
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Generally, you do not withdraw from a Stipulation. The matter was taken off-calendar so that you could attend the QME appointment, so you are now complicating your case. The Insurance Company could ultimately seek an Order for you to see a QME after a few months, but it is not wise to make them force you into an evaluation. Legal counsel is your best path right now.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.
Why would you want to withdraw from the Stipulation? First, it's probably not possible. Second, you probably want a QME evaluation eventually so why not get the process started.
The QME becomes the God of your case. Don't take picking your God lightly. You need to make sure you are in the right medical specialty. You need to make sure you pick the right doctor off of the list of three. Since you probably won't know any of the doctors on the list, you won't have read any reports from any of them; you won't have take the deposition of any of them; you won't know if they are more insurance advocates or injured worker friendly, how are you going to pick? Hint: retain a lawyer.
You need to consult with a good W.C. lawyer before you do anything else in this case that could harm you in the future. There are some great W.C. lawyers in the Sacramento area. Find a good one here at www.avvo.com or at www.caaa.org. CAAA is the association for attorneys here in CA who represent injured workers. Or you can call me for a referral.