In case you're wondering, this is almost always caused by improper pad geometry. From the pictures, it looks like there is a bit too much space between the 0402 pads.
Enigma
I was wondering about how far apart and big the pads are for 0402. This was the 0402 part from the Kicad library but I did at one point check it and it seemed to be right for at least some 0402 parts I checked against. But when I was placing them I thought these pads are far enough to take 0603 as well. Which is kind of dumb since why bother using 0402 parts if using as much space as 0603.
I only had 2 of those "tombstones" out of over 210 0402 placed so it's probably my placement inaccuracy combined with a wide gap between pads.