I have so many times this problem. I can clean the nozzle and the extruder, make the calibration, changed the extruder motor bearing, done the axis maintenance, changed thermocoupler but the problem is still there. Parts can be small or big , it makes no difference it stops when it should start to print horizontal thin lines.
How does the motor behave when the extrusion stops? Is it stuttering or rotating freely?
Also, once the extrusion stops - please, push the filament manually. Will the motor grab it and start extruding again? This could indicate the extruder motor is malfunctioning.
Motor is always rotating.
When this problem doesn’t happen I have a high percentage of completed prints, not 100% but near.
There’s something happening in that phase that get the filament stuck. If I push it, it then starts to extrude again