Error message when exporting a pdf for export

[pdh]

I get an error message every time I export using pdf for export. However, it will export if use export flatten. Though the flatten option takes a very long time.

It is a large document with a lot of scanned photos and documents.

Is there any loss in quality to using the flatten option? 

How can I get the export option to work.

[Lensman]

I (and others) seem to be having similar issues exporting a pdf from the latest version.  In my situation, I am not getting any error messages - just inactivity with no result.  It worked fine in the last version.  I realize this doesn't help any, but wanted to say that you're not alone.  I hope the Affinity Publisher crew is looking into this.