Maybe you can try this : Ionic / firebase stuck loading forever
The problem is not from firebase but from Ionic/Cordova, Ionic inject cordova automatically but after the firebase connection start (for my project) , this make that the browser stop and restart (for now I don’t know why).
If you add cordova.js at the top of your project, it will be fine, but for now the ionic will not work, you will have the same problem , since ionic doent upload the cordova.js file, didn’t find a way to get rid of that…