Since you know the QSECOFR password, you can login and reset the SST password for QSECOFR.
Login as QSECOFR and enter CHGDSTPWD then prompt F4.
Select *DEFAULT and press enter. This will reset the QSECOFR DST password.
As for the iNav error, we are only on V5R4 of iSeries Access for Windows so your options may differ.
Open iSeries Access for Windows.
Click on iSeries Access for Windows Properties.
Click on the Diagnostic Tools tab.
Select Detail Trace then click on Start Diagnostic Tools
Invoke the error then check your trace log. Click on properties to view the location.