I think this is something that does happen, it happened to me during the week. Its annoying, I think I have seen here that some people use felt pens to go over these small errors. As far as the woman in the shop - it happens with all threads and her comment is a cop out. I look forward to seeing what others say on this question and maybe we will have a answer

It looks very nice. I cannot see your "back thread, (which I am guessing means bobbin thread), but sometimes the tension may need a little adjustment if you are usng different threads. Perhaps someone with more techncal knowledge of embrodery will also answer and explain it better. But I think your sweatshirt looks great. Cpngratulations.

I have at least 2 bobbin casings, one I keep with a tighter tension for these kinds of designs. Always test stitch. Bobbin thread is different than embroidery thread. Great looking sweatshirt. Love the design.

It's a happy colorful design and you did a beautiful job on it. Sometimes it helps to use the same color bobbin thread as your top thread when using bright colors.

It happens sometimes, decrease the tension of your top thread 1 or 2 steps - on my Designer1 I always reduced the tension 2 steps for embroidery, don't have to do it on the Ruby. Never start fiddling with the tension of the bobbin thread if you can avoid it. The manual of my Brother 190D has instructions for this complete with pictures of the back, have a look at your manual, it's in the trouble shooting part of it.

Very nice sweatshirt.

This happens to me also with my Brother. My dealer set the tension on the bobbin tighter. This did not get rid of it so she told me to use pre-wound bobbins. This does help. The bobbins she sells not Brother. Using the tighter bobbin and the prewound bobbins does stop it most of the time. I also had to buy a second bobbin case for regular sewing. I have had to use matching bobbin if the bobbin still shows. I cannot see the bobbin thread in your picture. It looks very nice. Joyce

not knowing what machine you're running, if it is a Brother, you should have received a medal weight (looks like a real fat washer) to check the bobbin tension. The instruction shoud be in your owner manual. Too loose tension, loose hooping, fabric w/too much stretch, wrong backing (just to name a few things) could cause the problem. As for Maderira thread, I use it. However, if you are winding your own bobbins, make sure you are usaing bobbin thread...it's a different weight from embrodiery thread.
Hope this helps. I have 3 machines..all Brothers.

Forgot to ask, did you use Solvy on top? It really helps with fabrics like fleece/knits/terry cloth where you can get too much pull on the bobbin thread. It helps keep your stitches on top of the fabric. Without it, the top stitches can be lost in the soft fabric. Unless I'm sewing on a dense woven cloth (like a duck cloth/denim)I always use solvy. I'm just a hobbiest, byt my sister is a pro and I get to pick her brain.
One think she preaches, is do a test show on fabric similiar to the final garment. Even the best digitizer can make a mistake. I rather use the thread then lose the garment. Besides, old thread will gets brittle/weak and starts to break so you don't want to store thread too long.

great job

very nice

very nice

this look real lovely zoefzoef
lol wat een naam heb je hier
hugs Sonja