Is there a way to ‘test’ the z-axis? I’ve just had 2 long prints (should have been 38+ hours) fail after about 12 hours when the print head hit the model and moved the print-bed…I can measure when the model shifted, and they both were 27.66 mm, so I’m suspecting an issue with 1 or both of the z-axis controllers.
It’s more likely a warping model than a defective z-axis.
Too hot temperature because of too low layer times or not enough cooling could easily cause this.
Z-hop could prevent this.
Here is a topic for better understanding:
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Thanks, I’ll read up on this…
BTW, this was with the Dual Extrusion module, using 1 PLA for the model and a different PLA for the support. As a test, I re-sliced it to use just 1 PLA for both model and support (using the right extruder), and so far, it’s past the 27 mm mark (which was about 12 hours in), and I’m currently at 61% finished and 24 hours 
Some additional info to avoid shifted prints when the nozzle catches some protrusion: Magnetic print sheet fixation