Comment 41 for bug 152537

If setting the apparmor profile to complain mode still makes it work, then there must be still some kernel messages about denied actions. Your recent debug log (thanks for that) has

  [Job 93] Unable to open MFP port device file!: Input/output error

But does not say which or where. It's a bit weird, since the current apparmor profile runs unknown backends (like mfp) without any restrictions.

Can you please do the following:
 * Start from a clean boot
 * Try to print something
 * Attach /var/log/kern.log here

Thank you!