scan ONLY possible from ADF on LaserJet 3330mfp

FYI:

Perhaps it works with HPLIP version 3.13.4

Currently I provide HPLIP version 3.13.4
in the "Printing" development project
of the openSUSE build service
for various SUSE distributions.

For direct access to the RPMs go to
http://download.opensuse.org/repositories/Printing/
and select what matches exactly your system and
your architecture (32 bit i586 versus 64 bit x86_64).

openSUSE provides HPLIP in the RPM packages
hplip, hplip-hpijs and hplip-sane.

See
https://build.opensuse.org/project/show?project=Printing
------------------------------------------------------
The "Printing" project may contain new, upcoming
software. Therefore the packages in the "Printing"
project might neither be in a stable state nor fit
well into currently installed systems.
Have this in mind if you think about to install
packages from the "Printing" project into your
currently running system.
Do not use "Factory" if your system is
not "Factory". Use the matching packages
for your particular system.
The packages in the "Printing" project are
only for testing, without any guarantee
or warranty, and without any support.
As an extreme example, this means if your
complete computer center crashes because
of those packages, it is only your problem.
On the other hand this does not mean that those
packages are known to be terrible broken but
they are not thoroughly tested so that any
unexpected issue can happen.
------------------------------------------------------

See also
http://en.opensuse.org/SDB:How_to_set-up_a_HP_printer

As you can see in the OP, I AM using 3.13.4

Scary!
I did read your OP but somehow my brain made "3.13.3" of it.

Regarding "one of the updates I got during the last months":
You could use a command like "rpm -qa --last | head -n 40"
to show for example the last 40 RPM package installs.

Now I did a downgrade to 3.12.11-2.2.1 an it works again.
So it's definitely a bug somwhere between 3.12.11 and 3.13.4 ..

When downgrading HPLIP helps (without changing other
software packages in the system), it indicates that the
root cause of the issue is actually in HPLIP.

I think you should file a HPLIP bug report as described in
http://hplipopensource.com/hplip-web/support.html