Having issues with beginning balance for reconciliation in QB 2016 for Mac

I was attempting to reconcile this month’s checking account and the beginning balance was off. I used time machine to narrow down when the beginning balanced changed. I have a version of the company file from 10/13/17 where the beginning balance is fine when running the reconciliation report, and on the version of the company file from 10/14/17 it’s off when running the reconciliation report. If I try to undo previous reconciliations over and over the beginning balance remains off by the same amount all the way back to the beginning of the account. This would lead me to believe the error is very early in the register, however if I run a balance sheet report in both versions of the company file up to a date of 9/1/17, they are the same, but different from 9/31/17. This leads me to believe the error is in September. I do see where the mistakes are in September, but I don’t understand why this is affecting the beginning balance on old reports. Is there a way to fix this without having to go back to the last known good version of the file and re-enter all data for the past month or so?