QB Issue Resolution:

It sounds like you may have duplicate transactions.  Delete the unreconciled ones.  Duplicates happen when someone enters transactions manually and then downloads them from online banking.

Resolution for Issue 'I think there is a bug in my reconciliation register. How can I resolve the issue of previously reconciled transactions appearing back in the register as unreconciled?' available: Yes (Solved).
Source: Intuit Community forum.

I think there is a bug in my reconciliation register. How can I resolve the issue of previously reconciled transactions appearing back in the register as unreconciled?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for reconciliation register
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for reconciliation register [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: