Exported Excel file corrupted

When I export the Excel file and try to open it, Excel shows me an error “The File You Are Trying To Open Is In Different Format than Specified By the File Extension”. When I open it anyway, the content looks similar to this: https://imgur.com/a/yrpXFCh

Two first cells contain this:
<br />
<b>Warning</b>: “continue” targeting switch is equivalent to “break”. Did you mean to use “continue 2”? in <b>/data/web/virtuals/215404/virtual/www/wp-content/plugins/advanced-cf7-db/admin/class/PHPExcel/Shared/OLE.php</b> on line <b>290</b><br />

I’m running WP 5.1.1 with PHP 7.3.

• This topic was modified 5 years, 10 months ago by Gwidion. Reason: configuration added