Layer Shifting on Qidi Tech 2

[Pelks]

I've had my printer now for about 3 months and have had problems from the start.
I'm new to 3d printing so forgive me if these issues are basic!
My Main issue at the moment is that the layers shift randomly. see Photo.
I have printed things that are perfect, but others are not.
I am using Simplify3d as a slicer.
My startup script is:
; **** Qidi Tech Right Extruder start.gcode ****
M73 P0 ; Enable build progress
G162 X Y F3000 ; Home XY maximum
G161 Z F1200 ; Home Z minimum
G92 Z-5 ; Set Z to -5
G1 Z0 ; Move Z to 0
G161 Z F100 ; Home Z slowly
M132 X Y Z A B ; Recall home offsets
M135 T0 ; Load right extruder offsets
G1 X-100 Y-75 Z30 F9000 ; Move to wait position off table
G130 X20 Y20 Z20 A20 B20 ; Lower stepper Vrefs while heating
M126 S100 ; Set fan speed
M140 S100 T0 ; Heat buildplate
M134 T0 ; Stabilize bed temperature
M104 S225 T0 ; Heat right extruder
M133 T0 ; Stabilize extruder temperature
G130 X105 Y105 Z40 A80 B80 ; Default stepper Vref
G92 A0 B0 ; Zero extruders
G1 X100 Y-70 F9000 ; Move to front right corner of bed
G1 Z0.3 F6000 ; Move down to purge
G1 X-90 Y-70 E24 F2000 ; Extrude a line of filament across the front edge of the bed
G1 X-100 Y-70 F180 ; Wait for ooze
G1 X-110 Y-70 F5000 ; Fast wipe
G1 Z0.5 F100 ; Lift
G92 A0 B0 ; Zero extruders
M73 P1 ;@body (notify GPX body has started)
; **** end of start.gcode ****

I have tried both PLA and ABS. Both types have these problems.
I have also checked all the belt tensions and it is fine.
I am also only using the right extruder.

Hope someone can help.
Thanks