Why does the cyclic pentazolate anion fail to undergo N-oxidization in oxone solution?

When the pentazolate anion (cyclo-N-5(-)) was treated with oxone, a peak of m/z = 86 was detected via liquid chromatography mass spectrometry (LC-MS), which is the same molecular weight as the pentazolate N-oxide anion. After separation we obtained a completely new structure consisting of NaN5, sodium acetate, and acetic acid with a confirmed molecular weight of 86 as an impurity peak in the oxone system.