frame.topmost().navigate({
    moduleName: "next",
    transitionAndroid: {name: "slide"}, // Not working
});

frame.topmost().navigate({
    moduleName: "next",
    transition: {name: "slide"}, // this works!
});

public _getNavigationTransition(entry: definition.NavigationEntry): definition.NavigationTransition {
        if (entry) {
            if (platform.device.os === platform.platformNames.ios && isDefined(entry.transitioniOS)) {
                return entry.transitioniOS;
            }

            if (platform.device.os === platform.platformNames.android && isDefined(entry.transitionAndroid)) {
                return entry.transitioniOS; // <-- SHOULE BE entry.transitionAndroid
            }

            if (entry && isDefined(entry.transition)) {
                return entry.transition;
            }
        }

        if (isDefined(this.transition)) {
            return this.transition;
        }

        return Frame.defaultTransition;
    }