Solo Vertical lift problems

Check F19 and F20 on the 579 board. Could be just a fuse issue.

If the fuses are blowing, the lift motor needs to be replaced. Unless the board has an internal failure then the board needs to be replaced.  Fuses don't blow for no reason. Google search for re-certified ziehm parts to get connected with a good reseller for a good price or reach out if you need more info

The Z drive has been very reliable. In my entire time working for Ziehm, I have only heard of replacing the Z Drive on 3 systems, and I was involved with 2 of them. You're correct, fuses don't blow for no reason, but there could have been a spike or something. I've seen gloves get sucked down in the miniscule space between the top cover and Z drive shaft, which could drive up the current and blow the fuse as well. I'm sure you've replaced a fuse without replacing a component before.

Fuses that blow from spikes are in-line on constant active logic on a board. In this case, a spike would not cause this due to fact that a motor doesn't draw current unless activated. And unless you are activating a motor at the time of a spike, a fuse blowing for this reason is highly unlikely.

To address the OP question in mored detail, if the motor is going one way but not the other, then it can be a simple switch issue. Or the cable has broken going to the switch that drives the motor down. There is only one fuse for motor power. And a blown fuse wouldn't product this result. It can also still be an on-board U579 board issue as well.

Oh and OP a couple more things. Check the U521 board, and the limit switches. If a limit switch is bad, this will also cause the motor not to go one way or the other if the circuit sees the switch is open.