Seamless mode "Repeat: mirror" option issue

[alexkiri]

As you can see in the following screenshot, the "Repeat: mirror" option seems to generate something peculiar for this particular image. When using the final image mirrored, it will appear that it has 2 spikes. The 2nd image was generated by creating a larger image from flipped copies of the original image, upscaling that with the seamless mode option set to "Off", and finally cropping to get to the original image size x4

Original image: