Does your PP put an M2 command at the end of the file?
According to LinuxCNC M2 does the following:
- Change from Auto mode to MDI mode.
- Origin offsets are set to the default (like G54).
- Selected plane is set to XY plane (like G17).
- Distance mode is set to absolute mode (like G90).
- Feed rate mode is set to units per minute (like G94).
- Feed and speed overrides are set to ON (like M48).
- Cutter compensation is turned off (like G40).
- The spindle is stopped (like M5).
- The current motion mode is set to feed (like G1).
- Coolant is turned off (like M9).
So as you can see M2 sets a bunch of stuff, one of which is G54 (P1).