swift2 - UIBarButton image drifts into position on when view is rendered -

i have several icons on toolbar. 1 of (highlighted in red) seem 'drift' position when view rendered if flexible space kicks in after image rendered. also, image kind of moves adjacent button's top left corner (the filter icon) position.

this happens if app launched when update became available while app either terminated or in background. while not understand why, seems rendering default icon in viewdidload, followed server status check , change of image sequence causes issue.

any thought might cause behaviour appreciated!

code simple:

    if newdataavailbleonserver() {      mybarbutton.image = cloudwitharrowimage  } else {      mybarbutton.image = simplecloudimage  } 

both images of same size , density.