Yes I have had that happen and my DH who repairs and refurbishes the older machines says it is due to the tension. Adjusting the tension always eliminates them for me.

Looks like a tension and/or speed issue. Going too fast on the curves will cause eyelashes on the curves. I can't tell from your picture, but if the bobbin thread is just laying on the back on the non-curved portions, it's a top tension issue. An incorrect thread path will cause this.

I have them too with my longarm. It's a tension issue.

The top tension needs to be tighten, as I am seeing not only eyelashes on the curves but also where there is more of a straight line.

I can sympathize...that's a lot of stitches to have to take out. Hopefully you can fix the issue before you redo it.

I believe that your top tension is too tight and you are moving too fast. On my LA if the top tension is tight and the bobbin to loose I will get eyelashes. Machines are very interesting. They all have there quirks. And they show up when you are in a hurry or on a dead line or otherwise stressed. Good luck.

I feel for you too. I think it happens to all of us. It is a learning experience.. I'm not sure if you are using a longarm or a domestic. I have a long arm and I take a mirror and look at the backside just to be sure I have no surprises. I also check my bobbin tension on every bobbin change.. If this is on the back side it is a top tension problem.. Hugs, it will get better..

Thread problems.
 

I find that if the stitches are messed up on the bottom the problem is the top thread and if messed up on top it is the bobbin that is not threaded right. If your thread tends to come out of the upper guides move where the thread is coming from. If you have it on the machine spool it will sometimes bounce and come loose. Also if it is a crosswound spool it should come off the top, not turning the spool. I keep a thread holder at my machine for the crosswounds.

Yes it has happened to me also more than once. It is irritating but it happens.

Yes, I bet we all have experienced eyelashes. Mine are often because of turning corners to quickly, so for me the by-word is slow down and not take the corners too quickly. But that is me and what I see on yours that is not the problem. Your turns are beautifully done. I think you solved you problem with the bobbin thread out of its guide. Ripping out is not fun but, it has happened to the best of quilters.