Full Power Without Motion is usually due to one of three things. 1.) Limit switch is tripped or noisy. 2.) DC servo power to the drive was removed. Here check the e-stop and DC power supply circuit. 3.) The servo drive is damaged. Probably not if intermittant though.
Most likely the problem is a limit switch. When digitizing the machine tends to shake a little and if you have loose or noisy switches they can trip just long enough to flag this error.