Ishoo is used, obviously, by those who feel slightly precious about using 'issue' - as if they're trotting-out a well-worn cliche. They want you to know they know it's a precious, up-oneself, pretentious, 21st-century psychobabbly cliche.
There's a wealth of hidden meaning and weight lurking underneath what you might think is a merely lazy, text-speaky mis-spelling.