If a cable loses integrity, where the broken strands are rubbing on the cable sheath helix, it's gonna-be sticky. My experience is that cables usually wear at the point of attachment where the ends are fastened. I would check there, so you have 8 points as there are two upper cables and two lower cables.
A pinched cable casing can cause stickiness, where the metal helix lumen (opening) is crushed onto the cable. The back of the service manual has cable routing instructions, and it's on here. http://vmoa.net/VMX12-Service-Manual01.pdf
Throttle cables need slack to operate without drag. You can prove this yourself by removing the slack, and experiencing the lack of the throttle to snap-shut. Introduce some slack, and the cable returns to normal function.
I use a clamp-on cable lube tool, into which you place a red lubricant wand, to shoot your favorite lubricant from a spray can. I'm partial to WD-40, but use your favorite snake-oil. I bet it's 40 years old, and it still works fine.