m5 extension board difficulties

[Mercury3D]

Hi,

I am utilizing the m5 extension board to add an additional extruder motor to my Ender 5 plus. I have all the slots on the main GTR filled. Because I have a wire too short I have added the E0 extruder to the M1 slot on the M5 board (not confusing at all, I know!...)
Although the E0 and E1 are the exact same motor and I have configured them similarly in the firmware, the E0 will not move when sent commands. Running an M122 shows this info:

_M122
axis:pwm_scale/curr_scale/mech_load|flags|warncount
Z Z2 E E1
Enabled false false false false
Set current 800 800 1000 1000
RMS current 792 792 990 990
MAX current 1117 1117 1396 1396
Run current 15/31 15/31 19/31 19/31
Hold current 7/31 7/31 9/31 9/31
Global scaler 133/256 133/256 133/256 133/256
CS actual 31/31 7/31 9/31 9/31
PWM scale 4294967295 7 9 9
stealthChop true true true true
msteps 0 64 64 64
interp true true true true
tstep 4294967295 max max max
PWM thresh.
[mm/s]
OT prewarn true false false false
triggered
OTP false false false false
off time 15 0 0 0
blank time 54 24 24 24
hysteresis
-end 12 2 2 2
-start 8 1 1 1
Stallguard thrs 0 0 0 0
uStep count 65535 2 2 2
DRVSTATUS Z Z2 E E1
sg_result 1023 1023 0 1023
stallguard *
fsactive *
stst
olb *
ola *
s2gb *
s2ga *
otpw *
ot *
Driver registers:
Z 0xFF:FF:FF:FF Bad response!
Z2 0x80:07:43:FF
E 0x80:09:40:00
E1 0x80:09:43:FF

Testing Z connection... Error: All HIGH
Testing Z2 connection... OK
Testing E connection... OK
Testing E1 connection... OK

This is showing two issues. The first:

sg_result 1023 1023 0 1023_

The E0 main extruder has a 0 for this entry. Even though it is being detected, its like its not being sent any power to move.

The Second issue is that the M112 command is showing strange readings for the first Z motor:
" hysteresis -end 12"
" off time 15"
" PWM scale 4294967295"
" tstep 4294967295"
" uStep count 65535"
"Driver registers: Z 0xFF:FF:FF:FF Bad response!"
"Testing Z connection... Error: All HIGH"

Both Z motors are responding to commands to move and seem to be working fine, but this entry suggests there is some issue going on.

My E0 driver is plugged into the M1 slot on the M5 extension board and I have configured it to use the following pins:

#define E0_STEP_PIN PF3
#define E0_DIR_PIN PG3
#define E0_ENABLE_PIN PF8
#ifndef E0_CS_PIN
#define E0_CS_PIN PG4
#endif

Any help you could provide would be greatly appreciated!