I would agree on the flare/internal reflection/refraction. A lens hood could probably help depending on the angle of your lens during the shot - give it a try. Maybe check there's no scratches or marks on the lens too - never know.
David Tran Sony a55 Sony DT 18-70mm f/3.5-5.6 Now sits as an antique as it no longer focuses properly. Wishlist: Sony RX10iv (or RX10v if it ever comes out)
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