Yes, I am experiencing this and have not found anything to solve this problem. Do you have proper authentication, DKIMSPF & DMARC setup for your domain? Have you tested this with something like http://mail-tester.com?
We have the same problem. SPF, DKIM, DMARC, all test passed. The problem is that, when the PDF is attached by phantomjs service, the mail is detected as potencialy dangerous. If the PDF is not attached, the mail is received in inbox.
Any advice to attach the PDF and going message to inbox?