Mautner's cleanness conjecture for 0-cuspidal pairs

Let $G$ be a group, let $\Bbbk$ be a field of characteristic $l$, and let $(C,\mathcal{E})\in\mathscr{I}(G)$ be a $0$-cuspidal pair. A prime $l$ is rather good for $G$ if it is good for $G$ and does not divide $|Z(G)/Z(G)^\circ|$. The pair $(C,\mathcal{E})$ is $l$-clean if the corresponding intersection cohomology complex has vanishing stalks on $\overline{C}-C$. Mautner's cleanness conjecture. If $l$ is a rather good prime for $G$, then every $0$-cuspidal pair $(C,\mathcal{E})\in\mathscr{I}(G)$ is $l$-clean. This is one of a series of unpublished conjectures by C. Mautner concerning modular reduction and cleanness of character sheaves; the source does not state whether the conjecture has been resolved.