asd-a2 e delta homing

hi guys
i have a machine with 5 asd-a2-E servos for over a year
two of my servos(Z &W axis) had problem in homing since begining. each time that a started machine and clicked on home all, all servos start homing as the order in ini file but this two drives shows as it is homed but they does not start homing. i had to click on home joint 1 and joint 4 several times in order for them to do homing . sometimes i had to do it ten times and some time just once . 
today , this drives did not do homing even after 100 times of clicking on home.
i reseted their parameters but it did not solve the problem. 
do you guys know how to fix this problem ?

i had to add that all their sdo's and register are like my other drives. xml of them are just a copy&paste of other axeses.
drives manufactoring date are different.

when i click on home these joints, their cia402.1.stat-homing becomes high and remains high
joint.1.homing becomes high and then low and joint.1.homed becomes high

status word and controlword changes for a short time and it should trigger the internal homing but it does not succeed doing so.