You can see in the pattern editor that the yellow focus corners are directly on the track outlines.
In the mixer, the top left focus corner is two pixels too far to the right. Also, the black spacing on the inside of the track outlines is two pixels on the left, but only one on the right.
The bottom left corner is two pixels too far to the right and one too high, while the bottom right corner is one too high.
This looks pretty weird when the focus is on another section.