A word to the wise for anyone experiencing this in Prusa Slicer or its derivatives, where your top layers of large flat objects get generated by extruding these weird discontinuous diagonal stripes that seem to get pathed out in random order.
Change you top layer pattern from "rectilinear" (which may be your default) to "monotonic."
This just took me a fair bit of fiddling to figure out, and I wasted an hour and some filament cranking out one shitty looking part. Apparently this model in particular causes this effect, which the slicer has never generated for me before. I have no idea why.
Maybe this'll save somebody from banging their head against the wall too hard.
Monotonic top layer setting is there exactly to mitigate this problem. The reason it isn’t default is because it requires more travel time so takes a little longer in some models.
It’s not a software bug, but a problem with the way speed/time-optimized paths fit on some models.