Without further ado, the following was found:

Issue:    According to above, a domain error also occurs when I<z> is a NaN?

"Domain error: \\f[I]x * y + z\\fR, or \\f[I]x * y\\fR is invalid and \\f[I]z\\fR is not a NaN"

"Domain error: I<x> * I<y> + I<z>, or I<x> * I<y> is invalid and I<z> is not a NaN"