I used to get this type of errors too (among other many errors), and then I discovered that the extruder motor tend to get too hot and the heat propagated to the extruder gears and to the filament, causing softening to the filament, and causing the jam in the extruder. My solution is to add cooling air from outside using an aquarium aerator through silicon tube and feed it directly into the extruder. Had zero trouble since.
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