With the chamber heated, a filament left in the toolhead path softens in the PTFE tube (PLA loaded, ASA print). After the first HOME, PRINT_WARMUP unloads the loaded lane when it is not mapped to the print's first tool (PRINT_START would swap it anyway). A failed unload stops the print before the chamber heats. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>