What's the version of your welder?
S-1
S-2
S-3
*look on the sticker in front face, lower right of the welder.
Or, start the welder into diagnosis mode. Power OFF > Hold Down PRM Select + Rotary Switch button > Power ON.
You should have the welder upgraded / modified if it haven't been done yet.
Else, sooner or later you'll have ERR701,702 and or 501 & a couple of weird behaviour.

1. Main Control Software v2.10
2. Motor Control Software v2.10
* In addition, some modification on some PCB inside.
p/s: contact your local Yaskawa/Motoman office. They should aware about this.
