I use the Amplisens magnosorb extraction kit and its multiplex HIV/HBV/HCV real time pcr kit. Everything was right until some days ago when it started to show strong noises for every sample in the green and orange channel. The NTC also shows S-shaped graph in the internal control. I have changed the microtubes, kits, and even the systems (2 Rotorgene Q systems), but the results keep repeating. Can anyone help me with a suggestion or probable reason?