Nozzles jammed after pause

Did little pause on print jobs, and both printers (M300 and M200+) were shut down about week. Today fired them up and start printing. Both printers started printing with clicking extruders. Changed nozzles, everything is fine and they are working again. Material what left on printers was ABS. Both external, one Gembird brand, other 3DJake EasyABS. So that problem cant be specific brand material dependant. But has anyone clue what happened? Why were after week pause both nozzles jammed???

Hi. As the material was left inside the extruder for a week, it seems that it could have got stuck inside the canal and clogged the nozzle - thus, the material leftovers prevented the filament from being extruded properly. Apart from replacing the nozzle, you can try to soak it in acetone.

Ok, but does once heated and then cooled down ABS transform to something what does not melt anymore? Answer is no.

But is there any tricks to prevent this in future? Any specific filament to load in when printers are shut down for weeks? Or is my case just something what is uncommon?

No, do not load any special filament. You just need unload the material when you plan a pause in your prints. In the meantime, you can soak the nozzle in acetone so it is ready when you plan to use the printer again.