Good morning guys! Thank you so much for taking a look and replying.
I hope I am understanding you right now. First, the soundSignal byte/integer: I have tried so many things to solve the problem, one of which was changing the data type back and forth. I must have forgotten to change half of it back. Now that I did, the problem still exists, sadly.
I have had a delay in ISR in my previous code too, as I wanted to control the lights timing easily and it didn't give me any problems. I2C is still not working though after deleting those delays.
I am sorry @Golam, I don't think I can answer your questions... What does "interrupt" refer to? Not the ISR? Do you mean the interrupting of my code by the error?