Since assembling my printer a few days ago I've been printing things non stop. This morning the extruder started making the sound towards the end of attached video. I tried using compressed air to clean out any dust or plastic bits that could be in there but that  didn't fix it. Any thoughts on what could be causing it to make that sound?

CR 10 v3?

interesting I was wondering about this also, mine makes the same noise when retracting, maybe it's normal

Yeah, v3. Just took the whole thing apart and didn't see anything obviously wrong except for a couple pla flakes.

Taking it apart and putting it back to together seems to have fix it.