Is it the bobbin hook?
 

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I have a Babylock Tiara. I bought it used from a dealer. Since I've had it, I have always had to constantly adjust the tension, even throughout the project. It's like Goldilocks. Not only do I have to fiddle with the tension, I will quite often get these huge loops of top thread in the back. You can hear this take place when it happens. So then I'm ripping stitches. Look at the bobbin area when this happens. There's a wad of thread (look at the 2 o'clock position in the photo) and notice the top thread is now behind the bobbin release lever. What is causing this and what can I do to fix it? Any and all suggestions are welcomed with open arms!

I know nothing about long arms, but I think that the hook is that pointy thing at two o'clock. What is supposed to happen is that the needle brings the thread down to the bobbin area where the hook snags it and wraps it around the bobbin thread.

Someone more knowledgeable than me will come along shortly.

bkay

When was the last time the check spring was replaced? This is the spring that is in the top tension assembly. Wondering if the dealer bothered to replace it when selling it used and even if they did, these springs need to be replaced on a fairly regular basis, it all depends how much use the machine is getting. And it is not out of the realm of possibility you have a defective check spring even if it was replaced with the dealer service before selling. I know of some LAers who replace them every 6 months and others who can go a couple of years. The loop of top thread on the bottom like you describe and picture is indicitive of the check spring needing replacing. Aside from that one area your stitches look great.
Other things that can affect your tension mid bobbin:
an uneven wind on the bobbin where tension has changed during the winding process. This can happen on prewounds as well as ones you wind yourself. I use magnaglide prewounds and I got rid of a lot of tension issues with this product. But even with magnaglides my tension varies between a completely full bobbin and one that is 3/4 used.
A blob of lint sloughing off and getting caught in your tension spring. This is a big reason the overwhelming majority of my quilting is polyester threads. Cotton, no matter how good will make a lot of lint with the high speeds these machines run at. Also you get lint from your backing fabric. I always notice a lot more lint when I have a flannel back quilt.
Quilt loaded too tight on the frame (you didn't say if this is table mount or rack mount so if this is a table mount machine scratch this suggestion)
Edited to add, you machine may be just a teeny tiny bit off in timing. Ask your dealer what needle size they timed it too. Usually timing is set for anything from size 14 to 18 but if you switch up to those much bigger sizes you might have issues. I usually quilt with a size 14 or 16 depending on what thread I am using and don't have to retime my machine.

I guess I should have titled this thread differently to: Is the bobbin hook causing this problem? ;)

You know, I wondered about the check spring. I will have to inquire with the dealer but I would suspect no as I've had these issues since I bought the machine. Also, I do notice how "things" seem to change depending on how full the bobbin is. It even sounds different, but no matter whether full, half-full or quarter-full, I'm having these slips as I'll call them. This machine is a sitdown longarm. I have watched Jamie Wallen's videos on tension, oiling, etc. so I have checked for specks of thread etc under the bobbin spring and try really hard to keep the bobbin area clean. Only thing I have not tried is the magnaglide prewound bobbins.
I notice, too, when using cotton batting that there is lint which is why I try to keep the areas clean to no avail.

Is it possible to send a picture via e-mail to your dealer tomorrow and get his/her take on it?

My Tiara makes a different noise depending how full the bobbin is, as well.

Watson

Sorry you’re having problems! Here’s my suggestions, hope they help.
1. Do you have a piece of thread stuck in the bobbin case? In the picture, I think I see a piece of tan thread at about 11 o’clock in the bobbin case.
2. When you place your bobbin, hold the thread like this:
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Then push your bobbin directly in. Never lift the lever to place the bobbin. When you pull up your bobbin thread, make sure it has not wrapped around the lever. Holding the thread like this helps prevent it from getting under the lever.
3. Completely rethread your machine. A lot of times the top thread will jump out of a disc without even realizing it, especially when changing threads and pulling them through.
4. Sounds like your bobbin winder may be winding unevenly if you’re having tension problems throughout your project. Have your dealer check it.
5. Check your bobbin for stray lint in the nooks and crannies. Trust me, this can definitely cause problems. Use canned air if needed.
6. Make sure there are no stray threads stuck in the inside section of the bobbin case area, as mentioned above. I once had a piece of thread about 6” long wrapped in there! If your machine bed has a removable section to access the bobbin area, take that off, too, and check for lint, threads, etc.

I never mess with check springs or any other part that would have to be replaced until I’ve tried all of the above and called my dealer if those don’t work. I’ve never had to replace anything yet....
Hope that helps, and good luck!

I saw that stray thread too. It could be causing your problems. Clean out your bobbin case with WD40 and them oil the bobbin case.

How long have you owned the machine? If fairly new to you, bring it back to the dealer and let them fix the problem for free. Also let them explain to you how/why the problem happens. Keep going back to the dealer until the problem is either resolved or you get a different machine. I love my Babylock Jazz and my local Babylock dealer. You can also contact Babylock directly and see if they can offer you any advice. Good luck!

Thank you so much for the tips. I've done all these steps to no avail.

The thread that you see is after I heard the snag. I have checked and rechecked the bobbin case and in the place where you place the bobbin and no stray threads. I can quilt along for about five minutes, sometimes ten, then I'll get this long top thread that gets pulled to the bottom.