StepperOnline A6 Servo

I don't use cia402 homing so someone else has to come with advice on that.
If you just want something that works you can use standard linuxcnc homing.
linuxcnc.org/docs/html/config/ini-homing.html

You can always revisit cia402 homing later on.
 

Er87.1 is "One-time excessive position reference increment". It sounds like your drives are trying to move from $home to the last commanded target position in one CSP period.

Try commanding the drive to find home using its CIA402 home method, and immediately (before the homing sequence finishes) set the target position to 0.

How can I adjust this?
I searched for this because it seems that other users had the same problem.
It was recommended to set the value HOME_ABSOLUTE_ENCODER = 2 and omit HOME_SEARCH_VEL; HOME_LATCH_VEL.
So I set the following.
HOME = 0.0                            
FERROR = 1000                        
MIN_FERROR = 1000            
MAX_VELOCITY = 100            
MAX_ACCELERATION = 750               
MIN_LIMIT = -1800                    
MAX_LIMIT = 100                        
HOME_OFFSET = 0.0
# Sequence for homing Start at 0                     
HOME_SEQUENCE = 0                     
HOME_SEARCH_VEL            = 1     
HOME_LATCH_VEL            = 1     
HOME_IGNORE_LIMITS        = YES
HOME_ABSOLUTE_ENCODER = 2
CIA402_HOMING_ENABLED = 1
CIA402_HOMING_METHOD=4
CIA402_HOMING_SEARCH_VELOCITY=100000
CIA402_HOMING_LATCH_VELOCITY=50000
CIA402_HOMING_ACCELERATION=131072

This now works for at least one axis, but all the others still malfunction.

 

Eureka!
I think I've found the cause.
While I was testing various settings in the ini file, the errors occurred sometimes on one axis and sometimes on another.  Even with unchanged settings, the error was sometimes there and then gone again. Until I turned off my handwheel (WHB04B). 
With the handwheel turned off, there are no problems with referencing. 
For some reason, the handwheel seems to interfere with the reference run.