I just went to my LA Club class today and tension is always a topic. The leader told us today you should always check the bobbin tension when you change a bobbin and adjust the top to fit the bobbin if necessary. I try to have a scrap sandwich along the side of my quilt to check my tension when I change a bobbin or see a problem.
I use magna glide prewound bobbins because I didn't get a bobbin winder when I bought my used HQ Sixteen. I use Superior threads but am going to start trying some new threads like metallic, etc. for some quilts.
Having a LA Club only a half hour from me is wonderful Those ladies solve so many problems for me. You should call HQ and ask it there is anyone in your area.