As far as I can tell, nothing seems to change it. It's always the edge of the print on the ink tank/cleaning unit side of the printer. Always on the edge of the printed image even if the page is turned long ways.
I virtually never use the VFA setting and when I do it's for something that I'm...
Only ever happens with the VFA setting and is generally very feint with no apparent impact on the actual printed image. It's out of warranty and I'm not following the DPR community's advice and throwing out the printer. 🤣
Because it's apparently media setting dependent, it's a strange behavior...
I'd be surprised if US 502 isn't the same thing as UK 102 with different keys on the bottles. I'm certain they never used to call it Claria and the spec sheets for the new printer models only call out the pigment black as "Claria ET". It's silent on the color dye inks.