OK great news! Following up so anyone running into this same problem and finding this thread will know the resolution.
I submitted a trouble ticket and the tech was able to tell me that there was a bug in the offline mode function present at the time of my release (2.9.6.58056 - July 2024). The tech said the offline mode bug had been fixed most likely in 2.9.15.9599.1 (released on 5/5/25) and offered a great suggestion to keep my old version and install a new version and compare their replay modes. Unfortunately I don't have the disk space to pull that off. That left me with no way to run offline mode with my July 2024 release, but updating held the risk that replay mode wouldn't be as accurate as what I experienced with 2.9.6.58056.
I decided to roll the dice so updated to the current release (2.9.19.13878) and offline mode worked as expected. Then I tested replay on a couple missions that I always had problems with and replay was solid so good news all around! Regarding replay, I should mention that 99% of the time I fly F18 carrier ops and rarely fly against the AI which is probably why my replays are very accurate.
Thanks to all who contributed to this thread...I'm off for a day of offline mode carrier ops!
WytchCrypt's post in Cannot Enter Offline Mode (Error 500 & 401) was marked as the answer