Export from Excel to PDF generates "UnknownNodeType" in tables

We're exporting a simple worksheet from Excel to PDF. In Excel, if we format the data as a table, some of the <TR> are converted to <UnknownNodeType> tags. However, if the data is not converted to a table, the issue does not occur but then we're unable to assign table header cells. For example, we're using the following junk data as a test:

This will generate the following (simplified) PDF tag structure:

<Document>

     <Sect>

          <Table>

          <UnknownNodeType>

               <TR>

                    <TH>

                         <p>

                              Header 1

          <UnknownNodeType>

               <TR>

                    <TD>

                         Data 1

We've tried exporting to PDF using Excel's built-in "Save as PDF" feature, and using the "Open" command in Acrobat Pro and both generate the same results. This issue also occurs on a brand new, blank worksheet so it doesn't seem to be related to any particular formatting, macro or other issue specific to the document.

We're not sure what else we can do at this point, and there doesn't seem to be much - if any - information on Google that replicates this problem.

Any insight would be immensely helpful.

Please let me know if you'd need any files for investigation.

Occurs in:

Excel version 1803

Acrobat Pro version 2019.010.20064