Pockets cutting too deep (repost)

Possibilities:

  • misconfiguration in Grbl (that should not be possible on an SO5 Pro, since the board is identified by CM and the HDZ is the only option
  • wiring fault — usually this is accompanied by an awful noise — power up, wait a bit and feel each connector, any which are warm/hot would indicate high resistance from a loose connection, check in w/ support
  • insufficient lubrication — make sure the linear rails/blocks are well-lubricated: CNC Machine Maintenance
  • mechanical interference causing lost steps on retract
  • as @arose87tags noted, possibly the tool loose in the collet and pulling out — use a good quality pair of wrenches to fully tighten
  • high tooling engagement causing the machine to be pulled into the cut, or to lose steps on retract — where possible avoid slotting and add geometry and cut as a pocket

and/or

and consider leaving a roughing clearance and taking a finishing pass.