I have 3 19XRVs in a plant that is 15 years old. 1 of the machines is showing a phase reversal error all of a sudden. I have checked phase sequence, compared CTs and Voltages at ISM. (PIC II machine). All parameters are normal. Machine started having Over Voltage issues; but, raised control level to 490 and that solved issue. Pulled ISM apart and checked all internals. Any advice greatly appreciated. This is the only machine doing it. Thanks in advance.