Created attachment 36093 [details]
Stacktrace

Hello,

I have a piece of code that I use to merge one excel sheet into a target Workbook. The code used is pretty much coming from the following resource: www.coderanch.com/t/420958/open-source/Copying-sheet-excel-file-excel.

While merging, an error is thrown by POI ContentTypeManage at:

if (this.container != null && this.container.getPart(partName) != null) {
			throw new OpenXML4JRuntimeException(
					"Rule M2.4 exception : this error should NEVER happen! If you can provide the triggering file, then please raise a bug at https://bz.apache.org/bugzilla/enter_bug.cgi?product=POI and attach the file that triggers it, thanks!");
		}

I tried to downsize the excel files used in my case, and I end up with the files attached:

- targetWorkbook.xlsm which will receive the copy of the sheet. This workbook contains a button (no macro attached anymore) and a picture.
- sheetToMerge.xlsx which contains the data to be copied in the target Workbook. This sheet at the time being contains only one picture.

Now, the code will work under any of the following conditions:

- Remove the button from the targetWorkbook
- Remove the image from the targetWorkbook
- Remove the image from the sheetToMerge

I have dug a bit in the code, and also checked the [Content_Types].xml files for all these workbooks, with no luck till now.

I attach the stacktrace, the code, and 2 files triggering the error.

PS: I am aware of the bug 62522; but I have reduced the files and the test case used to trigger the bug, and i believe that the premise of the bug opening was wrong. This bug is not solved if, i/o a jpg and a jpeg, I have two jpg, or two jpeg. Plus, the error is not triggered if the button is removed, but still we have both jpg and jpeg.