Gotcha! After going through a number of home and z-probe cycles I caught the culprit. A sticky z-probe pin. It only partially drops, so the switch is open when the sequence starts, moments later it drops all the way but by then it’s too late.
Here is a z-probe holder I used to replace the original one:
https://github.com/fredvj/Kossel-Mini/blob/master/Z-Probe/Z-Probe-holder.stl
You probably want to decrease the layer height when printing this part. Draft mode seems to be at least part of your problem.
Thanks Fred, I’ll give that a go. I didn’t print the original.
I had a lot of trouble getting this to be reliable. I eventually gave up. I attach a probe by hand, do the bed measurements, then leave them set. I altered Marlin to save bed-probe results in EEPROM. They seem to hold just fine for months at a time… so far.
@Aaron_Birenboim that’s what @Billy did on the ZeGo. Manual probe attachment works just fine. Nothing should change the readings, generally. Though I’ve found they need to be redone after belt tensioning.
@Fred_vom_Jupiter printed @ 0.1 layer height and fitted, that’s working far better. Thanks again!
Glad to hear the part worked for you. I created a blog post with the story behind it:
After installing my new E3D hotend I decided to take a closer look at the software side of this issue. The hardware is of course the first thing that needs to be fixed, but the software should handle a failure of the hardware if possible.
I have seen that you do have some experience with Arduino things. Maybe you can give this a try before I send a pull-request to @Think3dPrint3d :
This change will stop the printer if the probe does not deploy (or retract) successfully.