E.R.
I have a Brother sewing machine too. I have had it for 3 years, and I recently have been having trouble. I have noticed that my thread gets all tangled and the upper thread breaks.
Once my needle was getting dull, and when I put a new needle on it fixed the problem. Sometimes it is the tension (adjust the upper tension...only adjust the lower tension if nothing else is working and mark it so you can put it back EXACTLY if it doesn't fix the problem..it is factory set). But lately I have found that I just need to take apart the bottom section where the bobbin is and clean it really good. I work with a lot of fleece, so I was getting a build up of lint that was my problem.
But I think I am still going to take it in soon just to get a good cleaning and service.
I am very novice about sewing, so I read the book and surf the net and just play around with it. Some days I just have more problems then others....
For Velcro you are going to need a stonger needle (like one you would use for denim...)I would talk to someone at the fabric store and have them show you the needle you will need.
If the stich is falling out, then it is not going all the way through (I think). You might want to try and Lengthen your stich and loosen the tension...Velcro is VERY thick...that is why it is working on your test strip, but not the velcro. You need your test strip to be Velcro...
And if all else fails, you can by Velcro that is on a fusing strip. All you do is peel the back off and it is lightly tacky, and iron it on and it will make a permanant bond with the fabric!!