OperationStopped with copying excel worksheet to another excel file in Powershell

I have an automation Powershell script running for years. But in the running this month, it keeps reporting errors when tried to copy an Excel sheet to another Excel file

$excel = new-object -comobject excel.application
$excel.Visible = $True
$excel.EnableEvents=$False
$excel.DisplayAlerts=$False

....

48   #Copy Summary tab from each model to Golden Summary File
49   $sheetToCopy = $workbook.Sheets.Item("Scenario") 
50   $summary_sh1 = $summarywb.Sheets.Item(1)
51   $sheetToCopy.Copy($summary_sh1)

The error message was

Call was rejected by callee. (Exception from HRESULT: 0x80010001 (RPC_E_CALL_REJECTED))
At Z:\ScenarioRun.ps1:49 char:1
+ $sheetToCopy = $workbook.Sheets.Item("Scenario")
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], COMException
    + FullyQualifiedErrorId : System.Runtime.InteropServices.COMException

You cannot call a method on a null-valued expression.
At Z:\ScenarioRun.ps1:51 char:1
+ $sheetToCopy.Copy($summary_sh1)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

My script was running on Win10&Office2010. I also tried to run it on Win10&Office365 platform and got same errors. Since it worked quite well before this month, I am not sure whether there was Windows or Office upgrade on Microsoft side or changes on my company's IT configuration side.

I have a loop coding to run this logic for all Excel files in certain folder. The logic did not fail every time. It is like reported 3 failures while the other 2 succeeds. And the failure of prior excel copy() would not impact the success of excel copy() of following files.

Any insight or input is appreciated.

Thanks. Leal