optics – Would you consider this lens (Samyang 8mm CS II) defective?

I purchased a new Samyang 8mm F3.5 UMC Fish-eye CS II today. After I made my first shot with it I immediately noticed a flaw. At f/3.5 the flare of bright objects is shifted towards the bottom (and just a little to the left).

I have quite few lenses and have never seen such a thing, Only my old Revuenon 1.4/50mm does it but in very subtle way. The flare is shifted to the left and it is barely noticeable, in fact I noticed it after purchasing the Samyang, and the effect is negligible (just few pixels difference).

The lens is usable after f/5 and flare seems completely disappear at f/5.6 which effectively makes the lens at best f/5 8mm.

I don’t mind flares, if they are even around the object, but such flares makes photos just ugly.

Is this effect considered normal?

Here are photos made with normal position of camera and rotated. The camera is Pentax K5.

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