I am no prof so I could not help you. I hopen my information does help you, or those who could help you.
I am facing the same problems.
But I discovered that whem you start a update and Bitdefender seems to crash the update continous in the background.
Look in/opt/BitDefender/var/lib/scan/Plugins/ or /opt/BitDefender-scanner/var/lib/scan/Plugins/.
I think Bitdefender does not store the required environment variables in teh system.
And I think the problem is 64bit related.
I work with Ubuntu Studio 14. In 32 bit it works without any problem
In 64 bit I have the same problems.