Extend your commit date until you have something with every contingency that can be removed prior to closing ... already removed. A good buyer agent and atty protecting your interests should demand as much of your lender.
But in short banks go in their own pace.. They somewhat try to accomodate the closing date but when they can not as some of them are so big each department has a lot of backlog they do the best they can. Your loan officer should be the one who should be pushing for you. The other would be the closing agent.. They can also ask for documents and ask for when they will get them..
Sit tight and do not worry.. But pay attention to the contract you have and how they mention the commitment letter... What sales contracts mean with commitment letter and what banks mean are not one and the same.