Pong game issue with ball randomly accelerating

Python
1

I am currently following a tutorial for a pong game. The code is the same but my ball is randomly changing its speed and the left paddle does not work correctly. I can’t find any solution to it.
Here is the code

 #Pong game

import turtle

wn = turtle.Screen()
wn.title("Pong game")
wn.bgcolor("green")
wn.setup(width=800, height=600)
wn.tracer(0)

# Paddle A
#object
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
# Possition of paddle_a
paddle_a.goto(-350 , 0)

# Paddle B
#object
paddle_b = turtle.Turtle()
paddle_b.speed(0)
paddle_b.shape("square")
paddle_b.color("white")
paddle_b.shapesize(stretch_wid=5, stretch_len=1)
paddle_b.penup()
# Possition of paddle_b
paddle_b.goto(+350 , 0)

# Ball
#object
ball = turtle.Turtle()
ball.speed(0)
ball.shape("square")
ball.color("white")
ball.penup()
ball.goto(0, 0)
ball.dx = 0.2
ball.dy = -0.2

# Function paddle_a
def paddle_a_up():
    y = paddle_a.ycor()
    y += 20
    paddle_a.sety(y) #setting y to the new y

def paddle_a_down():
    y = paddle_a.ycor()
    y -= 20
    paddle_a.sety(y) #setting y to the new y

def paddle_b_up():
        y = paddle_b.ycor()
        y += 20
        paddle_b.sety(y)  # setting y to the new y

def paddle_b_down():
        y = paddle_b.ycor()
        y -= 20
        paddle_b.sety(y)  # setting y to the new y

#keyboard binding
wn.listen()
wn.onkeypress(paddle_a_up, "w")
wn.onkeypress(paddle_a_down, "s")
wn.onkeypress(paddle_b_up, "Up")
wn.onkeypress(paddle_b_down, "Down")


# Maing game loop
while True:
    wn.update()

    # Move the ball
    ball.setx(ball.xcor() + ball.dx)
    ball.sety(ball.ycor() + ball.dy)

    # Border checking

    # Top and bottom
    if ball.ycor() > 290:
        ball.sety(290)
        ball.dy *= -1


    elif ball.ycor() < -290:
        ball.sety(-290)
        ball.dy *= -1


    # Left and right
    if ball.xcor() > 350:
        ball.goto(0, 0)
        ball.dx *= -1

    elif ball.xcor() < -350:
        ball.goto(0, 0)
        ball.dx *= -1

    # Paddle and ball collisions
    if (ball.xcor() > 340 and ball.xcor() < 350)  and (ball.ycor() < paddle_b.ycor() + 40 and ball.ycor() > paddle_b.ycor() -40):
        ball.setx(340)
        ball.dx *= -1

    if (ball.xcor() < -340 and ball.xcor() > -350)  and (ball.ycor() < paddle_a.ycor() + 40 and ball.ycor() > paddle_a.ycor() -40):
        ball.setx(340)
        ball.dx *= -1