Why appears nav-decor after pressing back button?

I have a contact listing page. When I navigate to another page (like contact creation) and click back, the page is rendered wrong, how can see in the image.

Appear a new div with class ‘nav-decor’. Why?

I try to reproduce in codepen, but could not.

When i click in plus icon in tooolbar , I use a normal navigation, with nothing special, as can be seen below:

newContact(){ this.navController.push(ContactFormPage, {"contact": { phones: [], emails: [], addresses: [] } }); }

Before:

After Back
image