Hi Nick,
This is a common issue with analog drives. It is almost impossible to command exactly zero speed with an analog signal with no offset or noise. This won't matter when the servo is enabled because the servo will command whatever voltage is necessary to hold position. It is only a problem when the servo feedback loop is disabled. The only sure way to avoid creep is to disable the amplifier. If you allow KFLOP to enable/disable the amplifiers you can avoid this. You will need to add a watchdog loop that watches the axis enables and if any are disabled then disable the amplifiers.
There is also an Axis Channel OutputOffset parameter that can be used to reduce the creep.
HTH
Regards
TK