my brother cs6000i has done this from day one! For the longest time I thought it was just me being inexperienced but now I know better I am saving up for a janome!

You could try getting another foot that is not the snap-on type, so that it would be more stable. You just need to know if it is a high bar or low bar. There are lots of feet choices for sewing machines, perhaps this will help.

I have Brother QC1000 and I've read that Brothers are known for this...read after I bought!