Client has VBA digital signature being lost problem

Excel 2007 Error : ' the digital signature is deleted when Excel users tries
to save the Master Excel Spreadsheet.'

The digital signature appears to be installed on client's various PC
correctly, however after the Excel version 46 had more VBA on the Sheet Level
added in version 47 the error stated appearing:

' the digital signature is deleted when Excel users tries to save the Master
Excel Spreadsheet.'

Testing shows that by deleting all Large Amount of VBA from the Sheet Level
in version 47 and adding back in the VBA on the Module Level the:

' the digital signature is "not" deleted when Excel users tries to save the
Master Excel Spreadsheet.'

But when I add the VBA on the Sheet Level back into in version 47 the:

' the digital signature is deleted when Excel users tries to save the Master
Excel Spreadsheet.'

Came back. What gives? Can VBA on the Sheet Level be too large for Excel
2007 VBE. Anyone else run across this error.