Splitpane not showing menu correctly

Dear, this is weird, the splitpane is not showing menu correctly. the splitpane is controlled using boolean expression, any one help!

this is the partial code:

<ion-app>
    <ion-split-pane [ngClass]="data.theme" [when]="!data.isMobile && data.isSplitPane" contentId="menu-content">
    <ion-menu contentId="menu-content">...</ion-menu>
    <ion-router-outlet id="menu-content"></ion-router-outlet>
</ion-app>