Let $R$ be an integral domain, $\mathfrak{m}$ a maximal ideal of $R$, and $I$ an invertible fractional $R$-ideal.
If $x \in I \setminus \mathfrak{m}I$ and $a \not\in \mathfrak{m}$, do we have $ax \not\in \mathfrak{m}I$?
Equivalently, does $ax \in \mathfrak{m}I$ with $x \in I \setminus \mathfrak{m}I$ and $a \in R$ imply $a \in \mathfrak{m}$?
No need any assumption on $I$ like being invertible.
$I/mI$ is an $R/m$-vector space. (If $ax=0$ in a $K$-vector space, then $a=0$ or $x=0$.)