I have a Platinum and never had this issue. I guess I didn't read thoroughly enough because I've never dropped my feed dogs to clean the bobbin area - just take it apart and pick/brush out what I can. Another friend has an old Kenmore and was having tension issues and it was a teeny piece of thread stuck in the bobbin case. Took me quite a while to find it after fiddling with tension settings. Got out the piece of thread, reset the tension settings back to 'normal' and it was all good. Hence my suggestion to the Sapphire friend to clean the bobbin/upper thread areas.