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Open Payroll on the person and go to the Accumulator tab. Click on the History button. Group by the field AccNo and expand the needed accumulator.
Check and note down from what period the amounts are not correct.
Continue to Setup | Maintenance | Payroll Procedures | Rebuild Accumulators (No calculation)
Chose from what period to rebuild from, as noted down in point two, and up until the open payroll period and click OK.
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