I was printing PLA, it looks ok up to a certain height (although it was warping slightly), but then it becomes ugly.
I will do a test print of the same height, butaybe you already have an idea.
Maybe something got stuck in the nozzle, partly clogging it. Try cleaning it. A trick I often use is to start the nozzle preheating and then yank the filament out of it as soon as it becomes warm enough for that to be possible, that usually pulls whatever crud was stuck in the nozzle out along with it.
Depending on your printer the z axis lead screw might need cleaning and lubrication. I would get this on my ender 5 plus occasionally at a given height if the lead screw needed cleaned.
Looks like a clog, could be caused by too much retraction, too high temp combined with too low print speeds resulting with the filament being cooked inside the nozzle.