It looks like this could be caused by the solidify modifier on the icing object. If an object has vertices that are very close together the solidify modifier can produce strange results like this. Can you post a screenshot of the icing object in edit mode?
To fix this, I would try messing with the “Thickness Clamp” settings on the solidify modifier or moving vertices on the icing base mesh.
It’s also possible that there are overlapping vertices or bad normals at work here. To fix overlapping vertices, go into edit mode and select all (A), then search for “Merge by Distance”. To fix normals, select all in edit mode and press Ctrl + N.