[visual] 'Banana' flying across screen randomly

On both the PBE and Live servers I have seen what appears to be a stray part of the GUI flying across my screen. I have noticed no pattern in their appearance, it seems entirely random. I have sometimes seen 5 in one game, other times I go days without seeing one. They generally appear around the centre of the screen and fly in an upwards-and-right direction. They are generally visible for only about a second. I have attached screenshots I managed to grab on Live, it’s the same bug. (arrows are mine of course) Also, I have a friend who says that they have seen the same bug. I think my current live client was copied from them months ago, long before seeing this bug. Anyone else seen this?
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