No, i have not enabled debugging, there is no M111 command in my config.
; Configuration file for Duet WiFi (firmware version 1.21)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Fri Oct 05 2018 00:31:02 GMT+0530 (India Standard Time)
; General preferences
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
M555 P1 ; Set firmware compatibility to look like RepRapFirmare
;*** The homed height is deliberately set too high in the following - you will adjust it during calibration.
M665 R258 L398 B140 H377 ; Set delta radius, diagonal rod length, printable radius and homed height
M666 X0 Y0 Z0 ; Put your endstop adjustments here, or let auto calibration find them
; Network
M550 PSPARX3D ; Set machine name
M552 S1 ; Enable network
;*** Access point is configured manually via M587
M586 P0 S1 ; Enable HTTP
M586 P1 S0 ; Disable FTP
M586 P2 S0 ; Disable Telnet
; Drives
M569 P0 S1 ; Drive 0 goes forwards
M569 P1 S1 ; Drive 1 goes forwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards
M584 X0 Y1 Z4 E3 ; Apply custom drive mapping
M350 X16 Y16 Z16 E16 I0 ; Configure microstepping without interpolation
M92 X80 Y80 Z80 E100.48 ; Set steps per mm
M566 X1200 Y1200 Z1200 E1200 ; Set maximum instantaneous speed changes (mm/min)
M203 X18000 Y18000 Z18000 E1200 ; Set maximum speeds (mm/min)
M201 X1000 Y1000 Z1000 E1000 ; Set accelerations (mm/s^2)
M906 X1000 Y1000 Z1000 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout
; Endstops
M574 X2 Y2 Z2 S0 ; Set active low endstops
; Z-Probe
M307 H3 A-1 C-1 D-1 ; Disable heater on PWM channel for BLTouch
M558 P9 H10 F120 T3600 ; Set Z probe type to bltouch and the dive height + speeds
G31 P25 X-23 Y9 Z1.244 ; Set Z probe trigger value, offset and trigger height
M557 R140 S20 ; Define mesh grid
; Heaters
M305 P0 T100000 B3950 C0 R4700 ; Set thermistor + ADC parameters for heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C
M305 P1 T100000 B4388 C0 R4700 ; Set thermistor + ADC parameters for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280C
; Fans
M106 P0 S0 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P1 S0 I0 F500 H-1 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P2 S1 I0 F500 H0 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 power saving
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; Set voltage thresholds and actions to run on power loss
; Custom settings are not configured
; Miscellaneous
T0 ; Select first tool
M501
I think the problem is with repetier host, when i first make a connection with YAT , there is no debugging messages after when i connect it to repetier the debugging starts and restarting the YAT connection the debugging messages are continued until M111 S0 command is given.