I am trying to print a T-Rex skull for my son, but in the middle of the print, the filament stops coming through the extruder. I try to print something else and it prints fine. Then I go back to the skull and try it again and it does the same things. I tried printing a Einstein bust as well and it did it for that too. Does anyone know why this is happening?
It’s hard to say without more information but it could be temp related. For example, insufficient heat break cooling can lead to a jam on long prints due to heat creep from the hot end.
Does the filament stop coming out all together?
I do not know if this is your problem or not, but I had a problem with a connection where it would get hot and then sever the connection until it cooled off again.
I also once had a problem of the printing temperature was set too low compared to the preheat temperature.
Hopefully, your current is set low enough that the extruder motor is making a clucking noise as opposed to the extruder grinding filament or breaking quickfit connectors.
One reason some people have an extrusion problem is a partial jam causing filament not to come out as fast. I am not sure if that fits your situation or if the filament does not come out at all after a certain point.
Is the fail height on the t-rex skull higher than the height of the other test object?
I have realised that the friction between the spool and holder can play a role in filament getting stuck. So particularly with heavy spools, I always put a little Q20 oil on the area of the spool that makes contact with the holder. And I generally have much better results!
Like @Hermien_Pellissier I find that lubrication makes a difference. I’ve gotten in the habit of doing a drop of light machine oil (or, since I ran out, vegetable oil - now my prints smell like french fries!) at the start of every print, and at intervals through large prints. I printed a small in-line oiler that clamps around the filament and has a small bit of sponge in it, with a wide hole at the top so I can drop in oil on-the-fly.
Is it failing on the teeth? There are a lot, and if they are causing many retractions in a short period of time the filament could be getting too cool and causing the jam. In contrast a print, say a large square might only retract on the z-axis movement, so it does not have time to get as cool.
Maybe, as suggested above reduce retraction distance, not speed if that is truly the issue.
Filament? temperature settings? heated bed y or n? height of the failures?
@Patrick_Ryan French fries flavour! That is awesome! 
@PrintinAddiction idea should work
Thanks everyone for your help. I will try the suggestions and see if it works.
Check to make sure your hotend is not loose, something similar happened to me a while back. Would start ok and then the hotend would shift just enough to reduce the heat transfer and it would jam up, tightening the hotend solved my issue.