On Facebook I follow a page called Pfaff-USA since I use the Pfaff GrandQuilter. They had a great sewing tip that I had to try. We use both invisible and also fine thread when making our nautical signal flags. They both tend to try to wind off the bobbin when not in the case. Since we sew a lot I tend to like to fill the bobbins ahead of time. Their tip was to use toe separators and slide the bobbin in them with the extra bobbins you have so that they don’t unravel. I went to the dollar store and found the set below and took some pics.
The next picture shows the bobbins with one partially in. Since they are made out of foam they stretch and hold the thread in nicely. You can see the empty one since 2 come with the set.
For the sewers and quilters out there hope it helps!