We can talk about "the matter at hand" or "the matter at issue" and they seem to mean just about the same thing: something along the lines of "the matter currently under discussion." Is there a difference between these two phrases?
I think it's clear that "the issue at hand" is way better than "the issue at issue" but is there a reason for this?
Maybe you just want to avoid the confusion of using two meanings of a word so close to each other. Or maybe calling something an issue already implies that it is "at issue," so in that case saying "the issue at issue" would be redundant.