I have had a problematic Y axis since I got my Replicator 2 in April. The pulley set screw on the motor was basically a rounded hole when I received the printer, and so there was an inordinate amount of movement in the belt. I re-tensioned the Y-axis motor cable so many times that I split the motor bracket, and I've just replaced that, and tensioned the belt as much as I could, yet I'm still getting layer shifting in the first few layers of printing.

Below is the types of layer shift I'm getting:

1. Continued shifting for approximately 4mm Z, starting at ~40 degrees, turning a straight wall into a curve.
2. ~2mm shift between the 3rd and 4th layer of rafting.
3. Occasional jumps of ~0.5-1mm at ~4mm Z, only when using rafting

Some of the steps that I have not taken:

1. Switching the Botsteps to see if layer shift goes to X.
2. Ensuring the Y bars, that the gantry runs on are in alignment.
3. Getting someone else to tighten the Y-axis motor belt to confirm I'm doing it right.

Anyone have any experience with a range of issues, like the ones I've described?