lines changed from reconciled to unreconciled

[AIMAM]

hello,

A user complains that some statements lines for a specific bank account which were reconciled have changed its status to unreconciled in cash management.
The statement with bank codes "cheque" have not changed and are still reconciled.
That happened for all the statements that were uploaded to that bank account since JAN 2008.

Please help me. I don't know what caused the bug or how can I fix it..