I love mine but I also like working with knits to make and repair underwear and tshirts. That’s where they really excel. I’m working on a skirt now and debating if I want to do a French seam to make the interior look clean or just run it through the serger. Ultimately the serger would be faster and just as sturdy. They are kind of a specialty sewing tool and changing out the thread can be a beast but for certain tasks they really shine.
It might. Sometimes with knits, especially if you have the wrong needle or are really close to the edge, it can catch in the feed dogs and cause that problem. You can have similar issues if you have too much tension as well. Make sure to get an old Tshirt with similar fabric that you are retiring and practice some different zig zag stitches first. I keep sacrificial clothing around for practice stitches. You can also try adjusting the foot pressure to get it to feed more consistently.