Ender 5 lost Z position

[My Old Landy]

Today after a successful print, the Ender 5 decided that it didn't know where Y was and crashed into the gantry. The main board went into fault mode so I turned it off and back on again. Re homed it and it looked ok. Ran the leveling sequence and after the probe did it's job the bed raised up and crashed into the head.
Now, I have tried three times to sort it but to no avail. It crashes into the head every time.
The firmware is up to date.
The bed will not screw down further. I suspect that if I fooled it into thinking the bed was at a lower position the bed would still continue until it crashed into the head. There is no upper limit switch. It just keeps moving until I stop it manually. This has only started since it lost the Y position first.

Any ideas before I pack it up and send it back?
(I have printed a fair few things so it's not a setting in fact it doesn't get to printing as it crashes before the print sequence starts)

 

[daedalusminos]

I'd be checking limit switch/wiring (assuming it has one)

Is there a re-cal to run?

 

[My Old Landy]

I'd be checking limit switch/wiring (assuming it has one)

Is there a re-cal to run?

No limit switch. It has the height sensor and that works, it is the run to the bed that doesn't stop.
I am trying to run the calibration, it is crashing during that.

 

[Pilgrim22]

Try swaping the stepper motor from a different axis and see if the faults moves or stays on the same axis. you can do the same with the limit switch also.
Is the count direction for the y Axis correct ?

 

[My Old Landy]

Try swaping the stepper motor from a different axis and see if the faults moves or stays on the same axis. you can do the same with the limit switch also.
Is the count direction for the y Axis correct ?

I can try the motor swap. As I say, there is no limit switch in Z.

 

[My Old Landy]

Actually I can't as it is a double Z axis motor system.

 

[My Old Landy]

I have managed to reset it
I spoofed it by using a 20mm spacer. This set the bed far enough away that I could access the manual Z height adjustment.
It is now running again. I shall keep a careful eye on the Y to avoid another crash that could set it off again!
Cheers for trying to help