Picture box just fades out instead of moving. (Broken movement system) - vb.net

Question

I am trying to make a game in Win forms using VB from scratch which i know is a bad idea but i like the challenge. Therefore i have been testing movement systems so i can choose my favourite , however i have ran into an issue as trying to move with a picture box as when i press the movement key the picture box just starts erasing the image in the direction i wanted to move until it disappears.
I am using
Public Class Form1
Dim RightM As Boolean
Dim LeftM As Boolean
Dim UpM As Boolean
Dim DownM As Boolean
Sub Movement()
Do While UpM = True
PictureBox1.Top += -5
Threading.Thread.Sleep(20)
Loop
Do While LeftM = True
PictureBox1.Left += -5
Threading.Thread.Sleep(20)
Loop
Do While DownM = True
PictureBox1.Top += 5
Threading.Thread.Sleep(20)
Loop
Do While RightM = True
PictureBox1.Left += 5
Threading.Thread.Sleep(20)
Loop
Do While (UpM = True) And (RightM = True)
PictureBox1.Top += -5
PictureBox1.Left += 5
Threading.Thread.Sleep(20)
Loop
Do While (UpM = True) And (LeftM = True)
PictureBox1.Top += -5
PictureBox1.Left += -5
Threading.Thread.Sleep(20)
Loop
Do While (DownM = True) And (RightM = True)
PictureBox1.Top += 5
PictureBox1.Left += 5
Threading.Thread.Sleep(20)
Loop
Do While (DownM = True) And (LeftM = True)
PictureBox1.Top += 5
PictureBox1.Left += -5
Loop
End Sub
Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles Me.KeyDown
If e.KeyCode = Keys.A Then
LeftM = True
Movement()
ElseIf e.KeyCode = Keys.D Then
RightM = True
Movement()
ElseIf e.KeyCode = Keys.W Then
UpM = True
Movement()
ElseIf e.KeyCode = Keys.S Then
DownM = True
Movement()
End If
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub Form1_KeyUp(sender As Object, e As KeyEventArgs) Handles Me.KeyUp
If e.KeyCode = Keys.A Then
LeftM = False
Movement()
ElseIf e.KeyCode = Keys.D Then
RightM = False
Movement()
ElseIf e.KeyCode = Keys.W Then
UpM = False
Movement()
ElseIf e.KeyCode = Keys.S Then
DownM = False
Movement()
End If
End Sub
End Class

Answer 1

The question took me back to the Z80 days, I got a little nostalgic so decided to post a simplified answer.
'Position of PictureBox
Private Plocation As Point
'PictureBox Movement Boundries
Private XL As Integer 'X - Left
Private XR As Integer 'X - Right
Private YT As Integer 'Y - Top
Private YB As Integer 'Y - Bottom
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
'Set Boundries
XL = 0
XR = Me.ClientSize.Width - PictureBox1.Width
YT = 0
YB = Me.ClientSize.Height - PictureBox1.Height
'Position PictureBox roughly in the centre of the Form
Plocation = New Point((Me.ClientSize.Width / 2) - (PictureBox1.Width / 2), (Me.ClientSize.Height / 2) - (PictureBox1.Height / 2))
PictureBox1.Location = Plocation
End Sub
Private Sub Form1_KeyDown(sender As Object, e As KeyEventArgs) Handles Me.KeyDown
'Change X,Y depending on KeyPress
If e.KeyCode = Keys.A Then Plocation.X -= 5
If e.KeyCode = Keys.D Then Plocation.X += 5
If e.KeyCode = Keys.W Then Plocation.Y -= 5
If e.KeyCode = Keys.S Then Plocation.Y += 5
'Check for X,Y boundries
If Plocation.X < XL Then Plocation.X = XL
If Plocation.X > XR Then Plocation.X = XR
If Plocation.Y < YT Then Plocation.Y = YT
If Plocation.Y > YB Then Plocation.Y = YB
'Update Position
PictureBox1.Location = Plocation
End Sub
I'm intentionally checking all key presses one after another, helps with diagonal movements. It's a little choppy and basic but may give you some ideas. Happy programming...