Rhythmic clicking from the extruder. Pulled filament shows a flat, chewed section.
skippingticking noisefilament chewed flat
Ordered by how often each is actually responsible, not by how interesting it is. Work down the list.
The extruder is pushing against something it cannot move. Cold pull or replace the nozzle.
Excess retraction shears filament in the drive gear and causes the jam it was meant to prevent. Reduce distance first.
Slow down, or reduce layer height. Check against max volumetric flow.
Check the heatsink fan is running. Failures that start an hour in rather than at the start are almost always heat creep.
Raise nozzle temperature or slow down.