It's possible I made a spot invisible or inaccessible without noticing. I'll see.
e: Just checked all the spots. They're all accessible. There's a possibility you fell victim to a rare bug where a level 1 graffiti doesn't register as done.
I found the bug. There are in fact 126 graffiti spots, one is counted twice because it's made up of two linked spots. I know exactly which one it is, too.
