The 100 has low audio in the headphones and I believe that they only play on one channel in phones. In the past, we’ve suggested a booster like “The Boosteroo” or others when using headphones. The audio level is not adjustable either.
Try this: Switch Ch2 to another, non-working input. Can you hear Ch1 in the headphones? Now, switch and listen for ch2 in the headphones. This will tell if you’ve got both channels feeding the phones.
Record to tape using one channel and then the other. Plug a monitor into the audio and video out jacks and listen to the sound.
One other thing. When you hear a clunk from the camera as it’s tilted, that’s normal too.
The sound things were basically fixed in the 100A model.
Good luck Mr. Audio Engineer,
Steve W