If the growth is dying then you may cut it. It is also possible that this could be bacterial/fungal in nature. I have a recipe as follows: First, you will want to prime the soil with dolomitic lime, then spread wettable sulfur to Kill off any infection in the soil. I Also like to spray the plant itself. Mix a few drops of one or more of these ingredients into warm water with a spoonful of coconut oil: Rosemary oil, lavender oil, neem oil, garlic oil, cinnamon extract/oil and for really bad cases, also add clove oil.
Here is an article on their care: https://www.gardeningknowhow.com/ornamental/shrubs/potentilla/growing-potentilla-shrubs.htm