Carriage vibrations when moving in the -X direction Makerbot Rep 2+

[Lernerg]

Hello,

I have been using a makerbot replicator 2x at work for a few months now. It had been working smoothly, however recently it started to shake when moving in the -x diraction (from right to left). Does anyone know what the issue might be? Worn belt? Worn rods? Too much backlash? I have attached images showing that only one side of a printed part is affected. I am printing with MakerBot ABS @ 230C with a bed temp of 110C.

Thanks