Sorry, but if it’s a bug, nobody here will be able to fix it for you.
Apple don’t participate in this user-to-user forum. You can submit a report detailing your frustration, to Apple, using their feedback form:
https://www.apple.com/feedback/ipad.html
You won’t receive any reply, but we understand that all submissions are logged by Apple.
Alternatively, you can raise a case with the Apple Support team using the Contact Support link at the top-right of this page.
There is something that you could try as a possible workaround and alternative method of exporting to PDF. No guarantees that it’ll work for you - but it a method of generating a PDF from anywhere in iOS that has a print option.
From whatever App you’re using, select the Print option.
• When the print dialogue appears, in the first page image shown, reverse-pinch (i.e., spread your fingers) to reveal a PDF version of the page.
• Using the Share icon at top-right of this page, select Save To Files
• Choose the path that you wish to save the file