Guitar sound in “Lovesong” by The Cure

This is one of my favorite Cure songs and every time I hear it there’s this part that happens multiple times in the song, sometimes more noticeable than others and I’ve always wondered what exactly is happening. It happens at 00:21 in the song and throughout and I’ve always wondered is it a note or guitar flub that isn’t necessarily a flub cause it sounds deliberate. I’ve watched many guitar covers of the song just to try and see what they’re doing to make that noise, but no one does it.

Im not a musician and know next to nothing about guitars aside from understanding tabs and guitar/bass layouts. It’s actually one of my favorite small parts of the song as it adds a little ear perk up for me.