Hi.
I'm afraid I don't have a .csd to illustrate this; I can only recreate
it using [csoundapi~] with Pure Data, so I don't know if it applies to
pure Csound5:
the line:

outrg    17, aleft, aright

sends correctly to channels 17 and 18, but it also interferes with the
output of channels 1 and 2.  In anything more than tests, it crashes
Csound and Pd for me.
out32 seems to not have this problem; I can use outrg for channels
1-16, and out32 for 17-32, with no problems so far.
If needed I can try to make a file illustrating the issue without using Pd.

-Chuckk

-- 
http://www.badmuthahubbard.com