"Copy Sheet" activity not working when I change the file extension

I have an Excel file with .xlsm extension given by a customer of mine. We need to do some operation to the data on one of the sheets in that file, but it is protected and I cannot do anything directly to it. My idea is to create a copy of the sheet with necessary data on it, and save it in .xlsx extension. This way, I can do all kinds of operations to it (including Invoke VBA).

What I am doing is very simple:

Assign: originalFilePath = “C:\filePath\customerFile.xlsm”
Assign: filePathInXlsx = originalFilePath.replace(".xlsm", “.xlsx”)
Excel Application Scope (originalFilePath ) {
. . . . .Copy Sheet:
. . . . . . . . . .-(Property) DestinationFilePath: filePathInXlsx
. . . . . . . . . .-(Property) DestinationSheetName: “mySheet”
. . . . . . . . . .-(Property) SheetName: “mySheet”

All I am trying to do is, copy a sheet named mySheet in the original .xlsm file and save it into the same folder but with a different extension.
This works sometimes, but only sometimes. A new file does get created every time, in .xlsx extension. However, sometimes the .xlsx file created has nothing inside. Sometimes, it works fine with all data copied, but other times, it is blank inside. I thought they might be some lag, so I added a delay of 20 seconds, but it didn’t solve the problem.

Why does this happen? Is there a way to fix this issue or alternative ways to achieve what I want?