Printer stops for filament change

What is the problem?

My Prusa i3 MK3 (FW 3.9.3) run by OctoPrint (1.5.3) on OctoPi (0.16.0) has go a stange behaviour when printing ABS (from Prusa).
While printing a "one color only" object with a rather large footprint (8cm x 13 cm), the printer suddenly stops when printing the first layer of the infill (Gyroid, 50%) and asks for a filament change although there's no filament change command (M600) in the gcode (must believe me, code is too big to upload :wink:
This is behaviour is reproducible.
When I read the Terminal output I see strange "Recv lines" including M600 stuff (remember: not from the gcode!):
--------------------8<--------------------
Send: N17395 G1 X129.007 Y157.988 E0.00818109
Recv: ok
Send: N17396 G1 X129.023 Y158.257 E0.00702
106
Recv: ok
Send: N17397 G1 X129.157 Y158.526 E0.0078397
Recv: fsensor_stop_and_save_print
Recv: fsensor_oq_meassure_start
Recv: fsensor_oq_meassure_stop, 2 samples
Recv: st_sum=700 yd_sum=72 er_sum=0 er_max=0
Recv: yd_min=49178 yd_max=26 yd_avg=36 sh_avg=17
Recv: fsensor_restore_print_and_continue
Recv: Resend: 17396
Recv: ok
Send: N17396 G1 X129.023 Y158.257 E0.00702
106
Recv: ok
Recv: fsensor_update - M600
Send: N17397 G1 X129.157 Y158.526 E0.00783*97
Recv: echo:Enqueing to the front: "M600"
Recv: echo:busy: processing
Recv: echo:busy: processing
Recv: echo:busy: processing
Recv: echo:busy: paused for user
Recv: echo:busy: paused for user
Recv: echo:busy: paused for user
--------------------8<--------------------
What is going on here?

What did you already try to solve it?

  • printing from OctoPrint and from SD-card: same problem
  • changing filament: PLA works fine (but i need ABS...)
  • changing infill pattern: Rectlinear works fine (standard Gyroid pattern doesn't)

Have you tried running in safe mode?

no

Did running in safe mode solve the problem?

don't know

Additional information about your setup

OctoPrint 1.5.3, OctoPi 0.16.0, Prusa i3 MK3, firmware 3.9.3, Firefox 84.0.2, Windows 10 20H2

It seems to think it is the filament sensor that is detecting no filament - is there a way you can check this is working properly? Some of them have little LEDs on them to show there is filament present. Not sure about Prusa. It definitely seems the printer itself thinks filament change is necessary rather than OctoPrint/Gcode.