I just got my S1 a couple of weeks ago and it's been working beautifully - until today. All of a sudden, it's making a loud thumping/grinding noise at the beginning and end of each process. I've watched it while it's making the noise and it doesn't seem to be coming from the belts, but from the laser carriage itself. Everything is appropriately attached, cleaned, etc. and I can't figure out why it would have suddenly started doing this. 

Anyone else have this issue? If so, what's the resolution? Thanks in advance!