No, it was before printing started while the start code was running.
I hadn't changed the slicer start code; I'll attach it below and mark the spot where the head hit the bed with ***.
The phenomenon always occurred after successful homing of the Z axis. It didn't matter whether I used the file already saved in RS or a new file transferred from CURA. Restarting of the printer-board haven't helped. Only restarting RS cleared things up. After that, I was able to print the same, unchanged file without any problems.
So far it hasn't happened again. I'll keep an eye on it. Since you haven't heard of such an error either, it seems to be something very rare and therefore not really detectable.
; *** Startcode für P1_GEEE Umbau (240313)***
G90 ; use absolute coordinates
M220 S100 ; set Feed rate to 100%
M221 S100 ; set Flow rate to 100%
M204 S{acceleration_print} T{acceleration_travel}
M104 S{material_print_temperature_layer_0 * 0.80} ; set extruder temp stand by
M190 S{material_bed_temperature_layer_0} ; wait for bed temp
M211 S1 ; software end stops on
G28 ; home all
M400 ; wait for finished moves
M501 ; set config as active
M420 S1 ; use former generated mesh
G1 Z3 F3000 ; move print head up
*** here...
G92 E0 ; zero Extruder
*** ...or here the head crash into the bed ***
G1 X2 Y185 Z0.2 F4000 ; goto start point
M109 S{material_print_temperature_layer_0} ; set extruder temp
G1 E8 F2500 ; make a drop
G1 X2 Y50 E20 F1000 ; print purge line
G92 E0 ; zero extruder
