Your failure points are the control board, the stepper driver, the wiring, the stepper motor, and a mechanical issue. The majority of the time with issues similar to yours, the root cause is mechanical, but I cannot make a mechanical problem fit with the behavior. An intermittent wiring issue does fit the problem, and is the most likely culprit. It is rare for the stepper motor or the control board to fail.
If the problem occurs regularily, you can gain insight by swapping things around. For example, swapping the Z1 and Z2 cables at the control board and testing can indicate whether the issue is a driver or a control board issue, or whether the issue is downstream.