Oh wow - I can only imagine the horrors that went into producing such a broken file :)

I'm just a user of the library, but the code change looks good to me and includes a unit test and sample file. 👍

Can you tell me where in the sample file to find the errant <f>? I'm not seeing it in sheet1.xml. The last row doesn't seem to have any formula tags.

    <row r="34" spans="2:3" ht="25" customHeight="1" x14ac:dyDescent="0.2">
      <c r="B34" s="5" t="s">
        <v>24</v>
      </c>
      <c r="C34" s="4">
        <v>100</v>
      </c>
    </row>

Thanks for the second set of eyes @ms1111, the test file is actually an older version of the Manage My Money template from Microsoft. I thought the errant formula tag was after the cell in the row but perhaps not? I never converted it to an xml representation to see clearly where it is, but IIRC it might have been from the Chart Data formula.

Yeah, I don't know how all these wonky worksheets have wound up in the wild. The PR looks good though and thanks for including a test file that demonstrates the issue!