Thought I’d share this anyway, even if it’s already solved - might help someone with similar issues 
I was messing around with the hair, everything was nice and pretty, up until one fateful render where it all got messed up for apparently no reason - every hair was snapping to a random point in space. I even created a completely new particle system to test what was going on with default values, here’s some pictures:
And this is how it looked in the preview, everything seemed fine:
But then came the render to send it all to heck:
And to lessen my understanding even further, the mess transfered itself to object mode, until I swapped modes again or changed a setting somewhere.
Good news though, for it was no bug! Turns out I actually applied a remesh modifier just for the fun of it, and had it turned off in preview, because I didn’t quite like the look of it.
But of course, silly old me didn’t turn the darned thing off in the render, and it was the culprit all along.
Moral of the story, don’t mess around in your actual main file, or you might forget to undo all of the sillyness.