Unanswered Spool stopped feeding and caused yankage

Context: Using a Robo3D R1 +Plus

So I get my printer up and running, and I'm absolutely in love from minute one. I've primarily been using this old spool of white PLA I've had for probably a couple years in a dresser drawer (I know, the hubris, etc.) I noticed it was having a little bit of problem feeding, but it went away so I thought it was just a couple wrappings on the spool holder. I go to work and come back and:

Long story short, filament got jammed while feeding because I was away from home, came back to nothing coming out of the extruder and it looking like it was dragging stuff instead of extruding before it finished what would've been the print.

Now I can feed it and it has good clamping/whatever it's called (when I have my fingers loosely around filament being fed) and you can definitely tell it's the right amount of pull... But after a while, it goes to the bottom and even though it will feed, it will do it extremely less and slower (even when manually trying to turn the gear).

I'm trying to take apart as little as possible and still get this guy back up and running, so is this something as simple as running a guitar string through it until it goes smoothly, or is it indicative of a larger problem like stripped gears or something?