Not sure if this will be helpful for you or not - but we abandoned the built-in PDF generation a long time ago and started using api service: pdfcrowd.com - which has been extremely reliable (we run about 35,000 pdfs per month).
You call the API with a destination URL, which pdfcrowd resolves in real-time, and passes a PDF back.
I’d always thought we’d come back to Lucee PDFs - but it doesn’t sound like the right time for that yet.