That first layer is overextruded, either bump up your Z .05 or .1 or your flow or esteps is off.
If the clunk you were hearing is roughly halfway down the travel and you have one of the original kickstarter machines there was a manufacturing defect where the 2 leads were different pitch causing a skipped step about halfway down.
But that was a manufacturing issue and would not suddenly appear.
Did the clunk sound like anything in this thread?
Specifically this video:
Important to note is in the video when the clunk happens the whole plate moves, it’s not just a sound, it’s a large movement.