Reconciliations out

All my historical reconciliations are out. I worked back and found a reconciliation with a zero balance and unreconciled everything going forward. I completed the reconciliations again, that is two years' worth of reconciliations. I then ran another check and found more incorrect reconciliations even further back.  What do I do now? Should I unreconcile everything again back until 10th Oct 2018? Why and how did this happened in the first instance? All reconciliations were correct when completed.