Using my FlashForge Creator Pro tonight and, after a successful print (PLA), I began another one using the same filament. Checking in on it after about 1/2 hour, it looks like it laid down 3 or 4 layers and then stopped extruding. When I checked it, the plate was about .5 cm under the extruder. I tried reloading the filament but it seems like it's clogged although I can't tell by looking at the extruder tip. Could it be clogged inside? If so, what is the best way to go about unclogging it? If not, what else could it be?