problem in generating positive stable random numbers
From where did you get rstable()? It isn't part of R itself, and
poking around shows at least three different sources for it (CircStats, fBasics, stable (Lambert/Lindsey, not on CRAN)). I seem to recall that the third one also has a distribution function which is almost, but not quite monotone. The usual advice of taking package problems to the package maintainer applies.
I got rstable() from the fBasics package. Thanks.