First, start by adjusting the label spacers (collars) to ensure your labels don’t shift up and down. The collar’s job is to ensure the labels stay in place, so when the machine applies the label to the bottle or other packaging containers, it applies to the same spot every time.
Additionally, check the web path, and make sure your spacer bars are in the right spots. If they’re not in the right place, the liner may fray, which will then cause the whole label web to break. When this happens, you will either need to clean the machine or check if your spacer bars are set up correctly, and adjust accordingly.