everyone assumes lots of things . unfortunately - because of the companies dealt with - assumptions are perhaps the only solutionAmmonia sensor films have dye molecules embedded in a semi-permeable film. I assume that if the film is damaged by bending, scraping, cutting, or abrading, it is no longer semi-permeable and the dye can then come in contact with things that change the pH around the dye and turning it blue. Except for the Seneye film, I have accidentally snicked several different films and produced little blue marks. I have observed what you describe as well.