I thought all bobbin cases had "springs".. the tension spring is what you're referring to, right? I haven't found one yet that was in good condition that didn't.... All of the machines I've been using are metal bobbins in metal bobbin cases, with tension springs...
I will use a different sized needle next then to see what happens. I've been using s 90 / 14 universal. I will have to look to see if I even have a size 10.
Considering that the first machine I ever tried this on (A 290C, self winding horizontal bobbin, aslant, - talk about stacking the deck against yourself - a couple of years ago) almost went out the window, it's more than a little surprising that this would be "natural".
OK,.. I didn't even think about the bigger machines. I saw tutorials with LD using a Bernina or a Janome or something and figured that was a common machine for her.