With TPU in a nozzle heating to 150C the pressure kept changing for minutes (+43, then -56 as it oozed), faster than the sensor's own baseline update, and the guard stopped the printer at the start of z_check and home_xy with the nozzle in the air. Every ARM (also a phase switch) now writes reset_probe (register 52) and waits 0.2 s without reading, so only force during the guarded moves counts. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>