Bernina embrodiery machine problem
 

I'm embrodering letters and I'm using embrodiery thread in the bobbin(white) and it is showing through to the top. Using isacord thread on top. Can someone help me?

I slowed down my machine yesterday and it helped with this problem

Adjust your bottom tensions down a bit and see if it helps. Also use the same color in the bobbin as on top.

I have a stand alone embroidery machine. I hope my suggestions help you.
In the bobbin, I use thin BOBBIN THREAD or in a pinch Maxi Lock thread. If your bobbin is pulling to the top, your needle tension is too tight. When doing embroidery, you do not want tight needle tension. My tension is set to a 3 and sometimes 2 1/2. If the embroidery design is dense, I do slow down my machine.
You also may try using a second piece of stabilizer behind the project.

Are you using a thinner thread in the bobbin? If it is the same weight, use the same color. Otherwise, the thinner threads are usually white.

You need to lower your top tension, and if your machine has the option, thread the stitch finger on the bobbin case.

It also helps to make sure you have a new needle and are using the right kind of stabilizer.

Lower the tension.