The "key" to having keys made that always work, is: 1. Make copies only
from the original key, whenever possible.  2.  Have the copies made at a
lock shop by the experienced key cutter, not by the clerks in a hardware
store, lumber yard, or the key kiosk in the mall (unless a locksmith) 3.
If you don't have the original, have a new key cut to factory-original code
by a locksmith, and after the locksmith makes copies from this
new "original", put it away at home for future use in making copies (and as
your for-sure, always-there, back-up key).  4. Lastly, be driving the van
when you have the key made so proper function can be checked before you
drive off, just to be sure.

In the case of the Vanagon, for which key blanks are not always stocked,
even by locksmiths, save yourself some run-around time by calling around to
first determine who has the blanks, and whether they are the all-metal
blanks or the rubber-headed blanks, depending on your preference.  When I
needed additional keys two weeks ago, the VW dealer could only supply the
key blanks by special order, at $12.95 each, which I declined.  The
locksmith who had the blanks (all-metal) charged $3 per key, including
cutting (from my original).

Bill