When you say juniper, are you meaning ER Cedar (aromatic cedar)? ER
cedar has lots and lots of resin and, seems, to never really dry.
Those resins simply move, within the wood, as mercury in a
thermometer does.

Assuming ER Cedar: Those areas you are having trouble with will
always be problematic. You need really sharp planer blades and plane
as slow as possible. Make sure the blades remain clean of resin.
Similarly as green southern yellow pine, the resin will build up on
your blades and, even though they may be sharp, the build up doesn't
allow for a clean smooth cut. It is easier to see this kind of build
up (even minor) on jointer blades (readily exposed), than on planer
blades (hidden). ER cedar, being a soft wood, will not cut as clean
with "dirty" blades. "Dirty" blades will give the effect you are
describing, as dull blades will. Knots in ER cedar will sometimes
give similar problems, as the grain is oriented in several
directions.... like planing (or jointing) end grain.

Chip out may be a combination of several things: Feed rate, resin
build up on blades, dull blades, soft wood with grain in several
directions. A reasonable smoothening, or planing, then belt sanding
may be your best bet.

I am presently making side tables with ER cedar, slabs cut transverse
the log, hence face surfaces are end grain. These slabs have been air
drying for 10 + years. My procedure has been: Chain saw, disc sander
(24 - 36 grit), belt sander, hand sanding. I asked the local
Lafayette Woodworks (Lafayette, LA), if they had any better way to
smoothen these slabs. Their large wide belt sander was their answer,
but even when it came to final sanding, hand sanding, to get the
detail scratches out, was the final option/procedure. Again, this was
for all end grain surfaces. Here are some pics:
http://www.flickr.com/photos/43836144@N04/?saved=1

If not ER Cedar, then I may not have appropriate answers or
suggestions for you.
Sonny