What is going on here?

[taintedsushi]

First 3 layers go down flawlessly. The transition to the 4th layer however gets thrown out of alignment as a result of this chattering travel along the y-axis.If I rotate the model 90 degrees then the chatter occurs along the x-axis. can't figure out why this is happening other than that the travel speed is too high which is odd because it's the default 250mm/s that it's been all along. It's printing big models that's the problem since the travel speed gets ramped up. Smalls stuff prints just fine.The nozzle isn't catching on anything when it does this.If you turn the steppers off, both x and y move freely without binding anywhere.Belts are tight. Gantry is solid. Eccentric nuts are snug without being overly tight. Everything seems good.I even replaced the y-axis stepper motor. No luck.Any suggestions would be appreciated.

[taintedsushi]

Going to answer my own question here.My assumption that a snug eccentric nut was a good thing was wrong. One of the y-axis rail eccentric nuts was a bit too tight so easing off on it fixed the issue.I would suggest that when you are adjusting these, run the axis at 250mm/s (15000mm/min) back and forth to make sure it is running smooth.You can use the G-Code command: G0 F15000 [axis][location] ex. G0 F15000 Y200