Reviewing through your description I would recommend submitting a case in your customer group as a next step for investigation by the next available member of our support team. When you submit the case if you could include the following it shoudl assist with their investigation.
1. Is the behavior limited to a specific PDF file?
2. A copy of the/a PDF file which exhibits the behavior
Many thanks for your reply. I will log this as a case as suggested.
Hive Support team