If you watched this while it was printing, I bet you saw the soft overhangs being pushed down as the nozzle moved along. Layers aren't cooling enough in between and you're printing on soft PLA. Like Roxy said, a lot of things can come into play here. In addition to what she mentions, you could force more layer cooling time by printing multiple copies or items at the same time. Another trick would be to increase the minimum print speed and increase the minimum layer time in the slicer, making sure it is allowed to move the nozzle off the print for a while if it has to in order to meet the minimum print speed and minimum layer time.

I've even salvaged the tail end of a few prints by following the nozzle with a flat bladed putty knife to pull some of the heat out of the PLA while the blade has it held flat. I've also used a light stream of air out of a compressed air can to help cool off delicate parts of a print - at least before I implemented a serious print cooler.