As Remi said, the employee's work schedule may be causing the problem.
Such problems happen when a PCR uses TSDIVI for the no.of hrs in the pay period and this may have been different from TSDIVP which is from IT 8 - field DIVGV (pay period hours). This difference is due to the employee having different no.of hrs in one period as compared to the previous or next one (not due to IT 2003 - but due to the type of PWS used). For more details refer to SAP HR portal, SCN or on google,
From payroll simulation log, post the full details of the function PARTT in sub-schema XT00 or ZT00), PCR's ZPPF & XVAL (or ZVAL depending on your schema), RT .
