When using decorative thread, or doing machine quilting a common complaint is that the thread keeps breaking. Here are a couple of ideas to use which I have found help.
First always change your needle. If the needle has even a little bend or nick it can fray the thread and cause it to break.
Next try using Sewers Aid. Apply the sewers aid to the spool of thread. Draw a line of the Sewer’s Aid from the top of the spool to the bottom of the spool of thread. This will lubricate the thread enough to sometimes keep it from breaking.
And my final suggestion is to add clear nylon thread. Thread both your decorative thread and the nylon thread through the machine at the same time and through the same needle. I have found this especially helpful when using metallic decorative thread.