That's all it was. I deleted both deploy and retract probe files from the SD and problem solved.
Thanks so much for that dc42. Because I was using the IR probe I never even looked at the deploy or retract so couldn't work out where the command to move outside of the soft limits was coming from and I never read anywhere in the G30 or G28 codes about deploying or retracting.
Thanks mate

I changed the offset when I was mucking about trying to find out what was going on.
I've changed it back to what it should be.

The problem is when I issue a G30 command my understanding was the bed would come up and trigger the probe at the current X and Y position. Is this not the case?

I have posted up the entire contents of both,

Thankyou

; Configuration file for Duet WiFi (firmware version 1.21)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Tue Aug 14 2018 09:06:02 GMT+1000 (Australian Eastern Standard Time)

; General preferences
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves

M667 S1 ; Select CoreXY mode

; Network
M550 P3d Printer ; Set machine name
M551 Pthequickbrownunicorn ; Set password
M552 S1 ; Enable network
M587 S"Pizza Oven" P"Pizza Oven" ; Configure access point. You can delete this line once connected
M586 P0 S1 ; Enable HTTP
M586 P1 S0 ; Disable FTP
M586 P2 S0 ; Disable Telnet

; Drives
M569 P0 S0 ; Drive 0 goes backwards
M569 P1 S1 ; Drive 1 goes forwards
M569 P2 S0 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards
M569 P5 S0
M569 P6 S0
M350 X16 Y16 Z16 E16 I0 ; Configure microstepping without interpolation
M92 X160 Y160 Z1600 E2000 ; Set steps per mm
M566 X900 Y900 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
M203 X6000 Y6000 Z180 E300 ; Set maximum speeds (mm/min)
M201 X500 Y500 Z250 E250 ; Set accelerations (mm/s^2)
M906 X800 Y800 Z800 E1000 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1 ; Set axis minima
M208 X250 Y250 Z200 S0 ; Set axis maxima

; Endstops
M574 X2 Y2 S1 ; Set active high endstops

; Z-Probe
M574 Z1 S2 ; Set endstops controlled by probe
M558 P1 H5 F120 T600 ; NAL changed probe type
G31 P500 X125 Y125 Z2.5 ; Set Z probe trigger value, offset and trigger height
M557 X25:285 Y25:285 S20 ; Define mesh grid

; Heaters
M140 H-1 ; Disable heated bed
M305 P1 T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280C

; Fans
M106 P0 S0.3 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P1 S1 I0 F500 H1 T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
M106 P2 S1 I0 F500 H1 T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 ; Define tool 0
G10 P0 X0 Y0 Z0 ; Set tool 0 axis offsets
G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C

; Automatic saving after power loss is not enabled

; Custom settings
M584 Z2:5:6
M564 H0

and for home all; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool on Tue Aug 14 2018 09:06:02 GMT+1000 (Australian Eastern Standard Time)
G91 ; relative positioning
G1 Z5 F600 S2 ; lift Z relative to current position
G1 S1 X255 F600 ; move quickly to X or Y endstop and stop there (first pass)
G1 S1 X255 ; home X axis
G1 S1 Y255 F600
G1 S1 Y255 ; home Y axis
G1 X-5 Y-5 F600 ; go back a few mm
G1 S1 X255 F360 ; move slowly to X axis endstop once more (second pass)
G1 S1 Y255 ; then move slowly to Y axis endstop
G90 ; absolute positioning
G1 X220 Y125 F600 ; go to first bed probe point and home Z
G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z5 F10 ; lift Z relative to current position
;G90 ; absolute positioning

I've just set up my coreXY and can home both X and Y axis but cannot for the life of me work out how to probe the Z.

The homing endstops are at the positive end of travel for both the X and Y and they home no problem but when I hit home Z the printer runs very slowly diagonally back to X/Y zero then probes the bed, the probe triggers and causes the bed to drop to its maximum and then for no apparent reason the head takes off in an X negative and Y positive diagonal until the carriage crashes.

I initially se it up with reprap configurator and have had this problem from the start.

Thankyou