Ugly bottom surface of prints. What changed?

The bottom surface of my prints has become consistently coarse with lines that are evident to sight and touch. These are ‘fails’ in my book as I cannot pass such prints on to clients. It appears that the z height is slightly too high - but this should be automated so I’m unsure.

Old models that once worked now consistently fail in this manner.

Does anyone have any idea what may be happening or what I can try next? I’m out of ideas and would be very grateful for yours.

Machine:

  • P1S
  • Firmware tried: current and current-1
  • High temp smooth plate
  • 0.4 nozzle

What have I done?

  • Tried multiple rolls of ASA and PLA
  • Cleaned print bed with soap and hot water (standard practice)
  • Performed cold pulls (standard practice)
  • Changed out my nozzle
  • Ran calibration between firmware changes and nozzle changes
  • Tried old, previously successful prints (now fail)
  • Created primatives in Bambu Studio for testing (fail)
  • Tried classic and arachne walls
  • Ran flow dynamics and flow rate calibration