First post here, so please forgive me for any silly mistakes.
Recently the y-axis (I think, forward-backward) has started skipping forward when printing the first layer of my print. It prints the raft with no issues at all, sticks the bed nice and flat and the raft is perfect every time.
Then it starts to print the actual item, but every time it starts to the print the back right corner the Y-Axis jumps or skips on the gears and makes a loud grinding noise. The amount it jumps varies on the print, but always jumps towards the front of the print. It doesn't matter on the size of the print or the position, it always jumps forward never back.
The printer is a Makerbot Replikator clone, from eBay. The X & Y moves the extruder. I have tried upgrading and downgrading the software (which uses Makerbot software) I am unsure if I can update the firmware.
Any help much appreciated.
UPDATE: Image has been attached of the failed part, excuse the colour, I use it for my test prints. This is orientation it printed on the bed. First 3 blocks printed fine, 4th one jumped It printed in the following order 1. top-left, 2. bottom left, 3. bottom right, 4. top right.