If you get into combat (or rarely not in combat) an icon of an rare will appear but NOT the whole "banner" until you're out of combat then whole banner comes up properly, however sometimes banner disappear and icon remains then eventually fade away

Same issue here, haven't found a reliable way to reproduce it.

This is because of Stanzilla/WoWUIBugs#295 -- 10.0 introduced a bug in player model frames which makes the models inside them have a separate alpha value to their parent frame. This then compounds with SilverDragon needing the popups to be secure frames, which means I can't just hide them when we're in combat, so I completely fade them out instead... and now the models aren't respecting that. Fortunately there's a workaround which I can use for now.

hey kemayo, the solution i've found is to add a :Hide() and Show() calls to the models, since those still work (but SetAlpha doesn't), using the Hide() might help you