Birds nests usually are an operator error, there are ways to avoid them. For any machine, it is important to sit down with the store and go through the machine and learn how that machine works. Read the operating books from cover to cover. Bobbins can be different on every machine you have, particularly with Baby Lock (drives me insane) and they can go in the machines differently. So many factors involved, and the dealer you have can mean a big difference. Another warning, some dealers sell the machines but have not gone through the required training on how to repair the machines. You can have problems with every machine brand you buy, so many factors. To be honest, some of the best machines I have had cost very little. I regret all the electronic machines that are out now, I used to repair my own machines.