I used to have loops appear randomly on the back also , the only advice I can give is it is a tension thing . You just have find the right spot for your machine and thread that you are using . I just kept messing with both tension until all worked out
Good luck just keep trying wish I could be more help to you
Hopefully someone will chime in that can explain how to adjust your tension to get it right
I read somewhere [maybe in my manual ] that loops on the back of quilt were caused by machine going too fast . I would call someone who knows like APQS tech help , don't go on my word alone , for I am a newbie .....
Carol
apqs milli
"sweet dreams":D