Intermittent Rear Z-Motor Failure at Startup - Core One+  

Intermittent Rear Z-Motor Failure at Startup - Core One+

Hi everyone,

We're experiencing an intermittent issue with our Prusa Core One+ and could really use some ideas on what to check next.

Problem Description
The rear Z-axis motor occasionally fails to "wake up" correctly during startup, causing the bed to tilt dramatically as the two front motors move normally while the rear stays locked.

(see video  ).​

Symptoms & Pattern
- Timing: Only occurs immediately after powering on the printer, only first use of the day
- Intermittent: Doesn't happen every time, but when it does, it's always at startup
- Once past startup: If the printer starts successfully, it runs flawlessly all day without issues
- Temperature: Printer is in an unheated room (~15°C ambient)

What We've Checked
- Cable routing and connections - everything appears secure
- Physical obstructions - nothing seems to be blocking movement
- The dust cover is visible in photos, but we verified it's not interfering (plus the issue occurred frequently before installation)

Any known cold-start issues with Core One+ motors?

We're running out of ideas and would really appreciate any suggestions from the community.

Thanks in advance!