I am testing my app on HTC One M8 running Android version 5.0.2. When an input field in the app loses focus, a white background is shown after the keyboard closes.
My background image is set on .scroll-content, so I don't understand why it acts like this on Android.
Check your ionic pane colour and view colour. You have different background colour so in the keyboard adjust pane mode the view gets resized (height-keyboard height) so when the keyboard goes off it shows the ionic-pane colour. So override the '.pane' background colour and see will it make any difference.
keyboard adjustment will work only if '.scroll-content' is present. By default ionic-content will enable this