Digital BW, The Print

Flaking I believe is due to poor adhesion of the inks to the paper.
Pigmented inks do not penetrate into the paper quite like more fluid
solvented inks (dyes) and their adhesion is rather tenuous as you can
readily see by running your finger nails even softly, on a print made on
Epson semi-gloss. With rough textured papers that have a relatively flat
profile adhesion should be easier due to the possibility of mechanical
adhesion taking place, i.e. adhesion that occurs as the ink pigments become
entangled in the fibers. (These fibers under some magnification can be seen
as a rough jungle.)  The longer that it takes for the paper to dry, the
better chance for the inks to flow into the fiber bundle and develop
mechanical adhesion.  Accordingly, it seems logical that higher humidity in
the environment at the time the print is made will encourage mechanical
adhesion by allowing the inks to reamin fluid a bit longer before
solidifying.   If on the other hand humidity is too high, the inks may take
too long to dry and result in tracking.  Accordingly a humidity in the range
of 50% (the golden mean) and about 60% should be ideal.  If you have no
tracking problems but do experience flaking problems I'd go for the highest
tolerable (for printing) humidity but avoid higher humidities than 75% which
can bring about other problems. Temperature is another factor.  If the
temperature is too low the inks will not be fluid enough.  If your printer
has been stored in an unheated room just prior to use, you might experience
adhesion problems.  For temperature normal room temperature, (20 Deg. C),
should be ideal.  You may not be able to control all these factors unless
you have special facilities but at least, having a thermometer and
hydrometer where you print and keeping an eye on the environment will enable
you to develop effective and problem-free workflows.

Second, handling the paper with bare hands can easily interfere with
adhesion due to the greasy secretions from the skin which although invisible
can give you problems.  (for the same reason you never touch batteries'
terminals.  Accordingly it is best to handle the paper by the edges and
avoid touching the surface to print on or else wear cotton gloves while
handling.
Good luck!