The switch sequence in spindle switch/output switch operation is abnormal. The switching MC contact status check signal and command do not match. Check 24v to relays that control MC contactors. Check and correct the ladder sequence (high/low windings set correctly). Replace MC contactors, relays for contactors, or in rare instances I/O module with output to relays.
The switching contactors for high and low windings set incorrectly. Faulty switching contactors or relays that control contactors