Tab Panel icons show up during panel slide animation above it in sencha touch 2

Tab Panel icons show up during panel slide animation above it in sencha
touch 2

I have a tab panel over which I have another panel that slides up (using
animation type cover) and slides down using animation type reveal. When I
am checking my application in iOS6, the tab panel icons are becoming
visible on the sliding panel just before the animation starts.
Any help on this will be much appreciated. Thanks