We have one environment where the DynamicPDF converter fails to render PDFs if a PDF hasn't been rendered for a while. With logging set to 3 I can see that "Worker process started for WordConverter" but then nothing.
If we submit another document it works. We get "Worker process started for WordConverter" followed by "New conversion worker ready for: WordConverter" and then the PDF is rendered.
If we then wait a couple hours and submit another document, it fails again.