I sat down to try to explain but couldn't figure out the wording, so 10 minutes later, after pulling out scrap yarn and needles, knitting up a few stitches, watching the video.... Here goes.
That first stitch of the row is doing something different than the other stitches. The stitch is formed not only by the loops you made, but by bringing up the yarn from the row below... so you are actually carying a semi-complex weave of yarn up that elongated stitch.
If you watch the elongated stitch video from the site (not the scarf video), right at the end after she works the first elongated stitch, you'll see that that weird stitch is present in her work too... but the video cuts so quickly it's hard to really see. In the scarf video, you can see, if you look very carefully, that it does the same thing.
So basically, it's just a feature of the stitch.
When I made mine in fuzzy yarn, that wierd first stitch is completly obscured by the texture of the yarn.
In my test swatch, I was able to lessen the effect of that funky stitch but it ended up doing wierd things to the row below....
As for slanting, the stitches want to be very loose, and sort of slip down the long loops.... You can neaten that up by tugging the fabric down, and also by using your fingers to snug up the stitches against the needles by inserting your digits like a comb in the elongation and sliding them up to the needle while holding the fabric firm. It does seem to naturally want to be wonky, but gentle snugging and tugging seems to pull it back into shape.