Strange Things Outside of Shapes

Title may be a little confusing, sorry about that. Lately I have been experiencing this strange problem, there are unusal things if curves of two adjacent shapes are overlapping. I know they weren't there before but I am not sure when I first see them, maybe one or two months ago. Please see the images below, I am referring to jagged things just outside of each shape. When I export the design as png or pdf, they disappear but remain in the original file.