setRoot function does not load firebase data from the root page for the first time in sidemenu app


I am using a sidemenu app. I am setting the root pages using setRoot function in app.component.ts.
Whenever i select the corresponding menu item from side menu, the page opens up.
Now in that page i populate a list which is supposed to be populated dynamically from firebase.
The list is not rendered for the first time. If i select any other menu item and come back, the list is rendered properly.
Why is the list not rendered for the first time?
The setRoot function for each page is called from app.component.ts file. Is it the correct way?

Please find below the git repo link.

ionic info:

@ionic/cli-utils : 1.19.2 ionic (Ionic CLI) : 3.20.0

global packages:

cordova (Cordova CLI) : 7.0.1
local packages:

@ionic/app-scripts : 3.1.8
Cordova Platforms : android 6.2.3
Ionic Framework : ionic-angular 3.9.2

Android SDK Tools : 26.1.1
Node : v8.2.1
npm : 5.8.0
OS : Windows 7