After one-shotting a rock spiderling group with sculla's mace, the tactical battle hung. It could not be autoplayed, only autoresolved. Based on the way that other, similar bugs worked during the beta, I'm guessing that if a unit is shrunk and dies with the same action there is some animation snafu.
EDIT: Other things get killed when being shrunk by sculla's mace just fine. No idea why the spiderlings were special.