down scaling image leading to animation problem in pygame

Question

I have just started learning pygame and I'm trying to make a simple pong game. I load this image and scale it down to 20% of original size (the image was too big).

   self.image = pygame.image.load("assets/pads/sprite_1.png").convert()
   self.image = pygame.transform.rotozoom(self.image, 0, 0.2)

When I try to move the pad, it leads to glitches in the animation. But it happens only when I scale this image down to 20% or less. I think scaling the image is causing this error. Any thoughts on why is this happening and how I can make it work?