But an exact explanation as to why the game glitches in this exact way? Some questions just don't have answ-
The tail wag sound effect is written (B0), then the 1-UP (40) is ORed, resulting in F0. It writes the wrong "length" for the 1-up, and as it reads bytes in reverse, the beginning is broken instead of the end.
I love that the Internet is home to people devoted enough to explore these sorts of things. "Video Game Archaeologist" isn't a real job title yet, but it definitely should be.