When interacting with an ItemStack of fairy lights identical to the ones being looked at in-world, the mod still attempts to "replace" them, and plays the replacement sound. This occurs in both survival and creative mode. A recording of the issue has been uploaded here, where the sound is played each time the fairy lights are right-clicked.

Mod version: 2.1.2-1.12.x
Forge version: 1.12.2-14.23.4.2744

Finally got around to this.