Have you tried to adjust the source region or the render geometry in your sprite? They are in the section labeled “2” in this image. I got the image from here… Sprite Editor Reference | Unreal Engine Documentation
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You probably need to decrease the height of the region by a pixel or 2. This goes a little bit into defining the source region, but if you go into that area in the editor it should make sense.
https://docs.unrealengine.com/latest/INT/Engine/Paper2D/Sprites/RenderGeometry/index.html