Hello, Fili here :)
I had a little problem with my sewing machine a few days ago: the thread was a little loose every time I sewn thick fabrics. I checked the sewing machine parts, cleaned it, changed the needle but the problem was still there. Probably it's because my sewing machine is already very old. After several times failed to top stitch a bias binding, I thought it's time to give it a rest and do a hand stitch instead. I still haven't master the technique to create a neat and flawless hand stitch, not to mention it takes me hours (two to four hours!) to do a hand stitch.
And this is the result of my hand stitch:
I looks better than before, isn't it? The valley and hill wasn't as rough as before (see my previous hand stitch) and I must practice to sew faster.
That's it, see you later!