I had a birds nest yesterday. When you use Poly threads they do not break cleanly. So when I cut the birdsnest out there were an unusally number of thread splinters at the back of the hook assembly. I attribute this to the small size of the bobbin casing. However the small size of the casing is what attracted me to the machine in the first place. I spent 15 minutes throughly cleaning this out. My two cents is that every one keep an eye out for this. Because thread build up on the shaft can cause the hook in any machine to head or malfunction. All our other machines get seriviced at least once a year all though the usage is not heavy because I am a single owner operator running two four heads plus the new Amaya. When my machines are serviced the hooks are taken apart sanded and re-assembled. Any build up of thread on the shaft is cleaned out Anand