The only thing that I can think of is there must be debris and/or cuticle left behind on the nail plate. You really have to ensure that the plate is squeaky clean. I dont work with LCN but a friend of mine does and she is the best in her area and all thanks to training with LCN, it is a good brand! Sorry if Im not much help
Edited to add*
Now that I have seen the enlarged picture, it also seems that the product is coming into contact with the skin
Cleen Cheeks Spa