That tells me your tension is off somewhere. It can be frustrating when your machine isn't working properly especially when it feels like you've done everything. At any rate I'd you're free motion the feed dogs aren't an issue. I'd suspect bobbin tensionAt first, when I began free motion, it looked okay on front but was nesting on the back. And yes, new chrome topstitch needle, newly wound bobbin, checked how I threaded it, full small cone of Isacord thread top and in bobbin.
It began to not pull up the bobbin thread to the top, then when it did and I started quilting, it didn't connect with the top thread at all to make stitches. What is weird is that I tried just stitching with a regular foot and feed dogs up (when they worked) and it did just fine. I have no idea what the heck is wrong. The machine has almost no time on it, but was not used for a couple of years, just sat in the table with the cover on it.