I'm having very weird stuff going on in Deep Sky Stacker

[HaleBopp2007]

Ok, so I was stacking some exposures of the milky way, and when I got the final image, the program shook me with a weird coma effect in the top right corner. No, it's not because of the lens as single exposures were perfect. 

Does anyone know what is this, and/or how to solve this horrible issue? 

BTW, this is the image with removed edges, but the effect is still there

[michael8554]

All the stars look elongated to me, not just top right.

More intriguing is the square "Stargate" in the middle of frame - I've stretched to make it more visible:

[Seelive]

Try changing the alignment method to bisquared or bilinear.

[happy-kat]

Have you checked the single frames to see if one has issues.

Are you using calibration frames, and have you checked if any, flats really, have issues.

To help with stacking you could select your best frame after registering to be the reference frame.

Do any frames have really low score, you could try exclude them from stacking.