That Bernina 180 is a great machine! If I were your Bernina dealer, I would want you to have a great sewing experience with it every time you sat down to sew. When we get complaints like yours at the store, it's time for a "sit down" with the tech. You need to bring your project to the store and sew on it while the tech is watching, and let them figure it out. It's probably something simple. Those machines are practically indestructable.
When it loops on the bottom, that usually means something isn't right with the upper tension. Or, with rotary hook systems, thread will tangle around the back of the hook and wreak havock with your stitch quality. To find the thread mess, take off the needle plate and look down inside. You can remove the thread with tweezers and a big pin or needle.
The new Kenmores aren't as great as the old Kenmores. Those old Kenmores are jewels! I like to rescue them from the thrift store, service them and sell them. They're worth a second chance.
Good Luck!