FSK 420 rail mystery

[pixelated]

I was making some cuts with my HK saw and FSK 420 rail today, and they were coming out not square.
So I checked it with my Woodpecker square and sure enough, the rail was about 3mm off with the movable pin set at 0 degrees.
I took the pin off to see what might be possible for adjustment, put it back on, tightened it down at zero, and now everything is square. [blink]
I am happy that it appears to be square now (haven't tried a test cut yet), but confused.

 

[ultane]

Following

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[HiCal]

Because the FSK rail only contacts the piece you are cutting in two points it relies on the edge being straight. If there is any unevenness of the reference edge you can get inaccurate cuts. Once in a while there will be wood chip that sticks to one of the stops that will cause a problem as well. Also check that the adjustable stop is centered in its notch. It can be slightly off one way or the other. It just takes learning the little tricks.

Cheers.