I had noticed on longer prints, regardless of seasoning or what material I used the hotend would partially jam and the extruder would click. I noticed the cold end fan which doubles as a part cooler seemed to be blowing the wrong direction (blowing out of the carriage vs pushing into the carriage). As a test I flipped the fan and all the clicking/jams seemed to go away. To do this test yourself. Power off the machine. Pull out the ribbon cable. next to where you pulled out the ribbon cable you'll see a socket head cap screw that a M3 allen wrench fits into. Remove it. Then you can lift off the white cover (its all one piece- the front lifts up and slide towards you, there are clips at the back that keep it in place). With that done you'll see something like this : Remove the two phillips screws on the green board so you can move it to the side and gain access to the hidden screw that holds the fan clamps down. Remove the hidden screw located under the green board and the screw directly behind the fan. You can lift everything far enough to flip the fan over. Re assemble everything and test. If it seems the fan is blowing the correct way you are good to go!