What can cause the 4-20mA signal to lock in at 20mA on the ATV61 or Eflex drives?
Altivar ATV61 Eflex
A voltage surge or spike on the mA input exceeding 7.9 V on this input will cause the analog input to jump to 20 mA and to stay there until power is cycled.
If the voltage surge/spike can't be eliminated by proper cable routing and shielding, or through the use of an isolator you can install a 6.8 V zener diode (available at most electronic stores) to prevent the excess voltage from reaching the AI2 input.
Put the cathode end (marked with a line) on the AI2 input, and the other end on the COM terminal.