Return Page Previous is not working with Service ITS in the portal

Hi

We have published several services ITS in the portal of ESS. However the Return Page Previous is not working with the UPGRADE of portal 7.5.

In the portal 7.4 and ECC 6.07, the system work fine.

With the portal 7.5 and ECC 6.08, the system not work fine.

In the t.code SICFàNameServiceàError PageàLogoff Pageà

var lastNavTarget = top.EPCM.getSAPTop().gHistoryFrameworkObj.TrackingEntryBack();

alert(lastNavTarget);

if(lastNavTarget != null && lastNavTarget != "") {

lastNavTarget.navigate();

}