I went through Denver MEPS last month but it took a long time to get there. I had a knee arthroscopy 11 years ago and they wanted documentation from the hospital and physician (that no longer works there) that did not exist. Throughout the process they were vague about what they wanted. Two recruiters (one retired during the process) both said that Denver is known to be difficult and we were close to trying a different MEPS.
Eventually I decided to schedule a current x-ray evaluation with an orthopedic surgeon (which was still not good enough) and finally a remote appointment with the original physician at his new practice. With letters from both, that finally got me in the door. In hindsight the arthroscopy was automatically disqualifying so perhaps they wanted me to get all the documentation lined up to submit for a waiver (which has since been approved).
Sounds like since they have your every record (I only submitted big ticket items) so you are getting extra scrutiny. Keep working through it but consider also trying another MEPS (my recruiters said Sioux Falls, SD is good).