While the filament thickness issues are certainly a red flag, I’ll offer a couple more things to check, based on my having the same issues a while back. I mean, you got some successful prints, and then things went bad. Sounds very familiar… I think I’ve actually had all of these problems at the same time before:
1) Check gears on your extruder drive and make sure there is no loose play at all in their movement. If either of the plastic gears turn independently of the other, or of the motor spindle, that’s bad. Even just a mm’s worth. In my case, the plastic at the center of the large gear started wearing out so that it wasn’t locked onto the hex screw holding it in place. So as a print extrudes and retracts, back and forth, it eventually gets to a place where there are so many retractions in a short period of time, that the gears are turning back and forth without actually driving any filament forward. I super glued it together long enough to print a new gear and mount it better (with a bead of super glue from the get-go.)
2) Make sure the hobbed gear is clean – grinding on filament fills the grooves and the teeth don’t grab like they used to.
3) Too high of a retraction distance. I’ve seen advice particularly about keeping the value low for PLA (1.2mm or less, YMMV), as it’s kinda sticky, and if you get too many retractions in a row (most slicing apps have settings for mitigating that situation), it can pull it up into the cold part of your hot-end assembly, cooling the PLA and jamming it up above your hot end.
4) Cross-wound filament. I often re-wind a new spool of filament manually onto another spool, because there are often spots where it’s been wound so tight by the manufacturer that the extruder can’t pull off the spool. Then it just grinds away on that one spot. But that problem would likely have been obvious.
5) A crazy thing I would have never guessed to try – I tried this piece of advice and it seems to be working – reduce the current to your extruder motor when using PLA (and back up again for ABS.) Go into your firmware and find the setting:
#define DIGIPOT_MOTOR_CURRENT {135,135,135,135,135}
and adjust one or both of the last two 135’s (extruder 0 and extruder 1.) “135” represents a value from 0 to 255, where in my Marlin firmware 135 => ~0.75A. I use 85 to have it pull about 0.5A. This will allow the motor to slip a little if it has difficulty pushing filament through the nozzle for a moment, rather than viciously grinding away at it.