Here's a cover gallery of my complete run of Page Publications' Red Sonja series:
#1, c.December 1977
#3, c.November 1979
#4, c.May 1980
The first three issues are regular/magazine sized and the rest are digest size.
These five issues reprint the complete Marvel Comics Red Sonja series. Each issue reprints three consecutive issues of the Marvel Comics series.
Given all the Marvel issues were reprinted it is unlikely that a sixth Yaffa issue was published, but it is possible.
Red Sonja #1 was recycled by Yaffa as an unnumbered $0.75 cover-priced issue. It is possible other issues were recycled either as unnumbered issues or retitled issues.