What it means Output current imbalance points to a ground fault.
Likely causes
Insulation damage
Long cable capacitance
Checks, in order
Megger motor and cable
Source
Source (reworded, not copied): ABB, ACS580 Standard Control Program Firmware Manual, 3AXD50000016097 Rev J (2025-10-01), Fault tracing. Official manual (PDF). Fault numbers and names can differ between firmware versions.