50mm Summilux lens flare.
One of the things I always find amazing is the amount of flare my old 1950's version of the Summilux manages to generate. It really hates any type of back light. That is one reason I much prefer to use the 50mm F1 Noctilux as a walk-about lens.
Typical flare from the Summilux (probably F4 or F5.6) out of camera.....
The 50mm F1 works much better: