@user_3809655571 : I think its filament from another print because sometimes fillament does not fully get out of the nozzle so try to replace nozzle, use the uncloging tool or do a cold pull to do a cold pull heat nozzle and feed filament then cool nozzle as taking out filament and do this a couple times

@B.Prints : it could be that the inside of the extruder is

@3DMax_A1 : i dont know but do you glue your plate? if yes mayby it is the glue or something

@dector_official : clean your plate

@McC4 : i think it is the filiment but have you tried mabye glueing the bored with printer glue that helps sometimes

@CurlyFries1 : Definitely some remaining filament from a previous print that wasn't purged out enough. Do you have an AMS, or just manual feeding?

@waylaidwanderer : Welcome to the Print Clinic! The most likely culprit here is a loss of first-layer adhesion, which typically happens when invisible skin oils on the build plate prevent the plastic from bonding cleanly, or if the nozzle is starting just a little too far from the bed on those initial passes. To help narrow this down, did this flat bottom section print directly on your build plate, or did you have supports enabled underneath it?