You say the filament just starts grinding. I’ve had perfectly good filament do this … if the part is requiring excessive retractions. Does this happen regardless of what kind of part you try to print? E.g. if you try to print one of the LulzBot calibration parts… or maybe a calibration cube part, etc… does it still happen?
If this is caused by excessive retractions then Cura has two settings that are meant to keep it from grinding on the same bit of filament.
In the Cura profile, the “Materials” section (only visible if you use “Custom” settings instead of “Recommended” settings) you will see a few settings to tweak retractions … such as retraction distance (on a direct drive printer that value is usually pretty low… between 1 & 2mm (e.g. 1.5). I also notice several profiles default the max retraction count to 99 and I usually dial this back to something closer to 10 (if a printer grinds back & forth on the same millimeter of filament 99 times it is GOING to grind a groove into the size of that filament).
If you hover over the max retraction settings, it will tell you it applies to the number of retractions that occurs with the “Minimum Extrusion Distance Window”. So for the profile I happen to have loaded right now, that “window” size is set to 2mm and I dialed the max retractions to 10. This means that it is only allowed to retract a maximum of 10 times along that same 2mm length of filament… any additional retractions will be ignored. But once it clears beyond that 2mm section, it can start retracting again.
Otherwise if it happens regardless of what you are printing … then I might even start to wonder if the filament is ok and try testing a different filament to see if it still happens.