Take it easy, @
crs one.
If you're frustrated finding an answer, it's equally frustrating for those trying to figure out a solution to what looks like something trivial.
I've tried your process checking all my settings as I go (even resetting my brush to default) and on different resolutions. Even at 300dpi the layer effect stroke turns out jagged.
But you say you've done this before with no problems. I can't recreate it so Im uncertain what you're settings would have been at the time you managed it.
Maybe its just me, but in some instances, the stroke layer effect gives me undesirable results. Which is why I prefer using the normal stoke function found in MENU.
I get this... for the second stoke (first one was stroke path) and it works at any resolution - better even at a higher setting. This was done at 72.
I'm aware that by using the layer effect, it can be edited later without damaging the image on layer. But until a solution can be found you have to be a bit patient as others (or even me) might still be trying or there are those who hasn't seen this thread may have a solution.
PS.... I also see you've got almost the entire Photoshop internet community involved with this. And they too are perplexed. Patience.... someone , somewhere may come up with a solution to this. Like the others elsewhere, I too am wondering about the discoloration artifacts in your sample images...... but that's not the issue here. First things first.......