This happened to me about a month ago!! It was horrible and took hours to figure out. I have a Brothers machine. When I changed out the bobbin, it did not set tension correctly. Yes, the thread was going thru, and I could see it, but it was kinda swingy( is that a word?) birds nest like crazy, Just keep taking the bobbin in and out, be sure and hold the bobbin in PLACE!!!!!! when ur setting ur thread. and really be careful when u feed it thru the auto-matic tensioner. really follow it thru! It would never work by just feeding it thru with the needle! that thread should be tight before feeding tru the needle/sewing part. If u have a brother machine and u can't get it to work, private message me and I would call u on my cell. PS if ur qa new sewer write down where every thing is set before u start adjusting the tensions!!!!!!

Yeah! sounds like a tension problem... BUT, a quick look for dust and debris under the presser foot area is my first line of attack. Good luck.

I was having the nesting underneath problem so I asked my instructor that teaches our embroidery and sewing club at out local sewing machine and fabric dealer. She said nesting below is due to improper threading above; to be sure the lever is up for the pressure foot and pull the thread tightly through from both ends so there is not any play in the thread, then put the presser bar down to sew. I hope this helps. Vernell in Austin

Another thing that can cause nesting is haveing the presser foot down when threading. If the presser foot is down the tension disks are together and the thread is just sitting on top therefore bad tension. So make sure your presser foot is up while threading.

ok this has happened to me just recently and I have been sewing for years but never had this problem. I checked everything I could think of the bobbin, top thread all looked OK so I even took the bobbin out un-threaded it and re done that. I took the whole machine apart and did the whole maintenance thing, you know the oiling, cleaning and such.
Started sewing again, after a few stitches it did it again. Hammer was ready to give it it's last rights then I looked at the top thread and found it had wrapped itself around the top guide in such a way that it formed a loop and would not let the thread run freely. I have never had any thread do this before but I had bought a large spool of serger thread so I wouldn't have to change it so often and it has been the worst thread I have ever had. I have even tried putting it on a thread stand by itself but it still tangles itself round different parts of the machine while I sew and every time I try to wind a bobbin it flings itself so wildly it is unbelievable. So I would check to be sure this is not happening to you as well.

Give your machine a good dusting with a large brush - especially in the bobbin race, and make sure that there is no hidden bit of thread caught there. Change the actual bobbin as well. Change the needle and make sure you re - thread from the beginning. If nothing is hindering the flow of the thread, you may have lint in the tension disc.

Ditto and also use a walking foot if you have one.

An old friend of mine told me that to cut your thread from the spool, and pull the thread thru, which is like flossing your machine. Then take the bobbin out, and clean under and around your bobbin area. Then change the needle and thread your machine. Next, is put your pressure foot down half way, if that is required on your machine to free motion quilt. Bet the problem will be solved.

My thought also. I would even do further and remove the plate and get all the accumulated "stuff" out. Might be worth a service call for cleaning.

Also, you might want to start with a "thread saver".
When you come to the end of a seam, run a scrap fabric through and snip your initial piece off, leaving the scrap under the needle. When you begin to sew your next piece, there will be no loose thread to get caught and create your "birds nest".
Good luck.

Clean it, oil it, rethread top and bottom, then try adjusting the tension if none of that works, otherwise, you may need to have it serviced. Good luck