While I love Marlena, and know how great she is, there are other customer service people at US. You can also use
customerservice@ultrasabers.com or
info@ultrasabers.com.
I suggest the first, especially this time of year, as, you know, Marlena may take some time off for the holidays. And we don't want to send ALL of our support issues to her, because then she'll be buried, and the rest of the CS staff will be just sitting around.
Next up, the saber. Yes, you have an Obsidian LITE sound card, as the Obsidian v3 and v4 cannot run on AAA batteries. However, any AAA batteries should work for you, even ones from Aldi (we have those where I am too). I do suggest trying some name brand batteries, mostly because sometimes "new" generic batteries don't have a full charge.
One thing I've had happen is the ends of the battery pack can crack, and so the batteries actually aren't in as tightly as they might look. Check the ends to make sure they aren't bent outward slightly.
There are only two things I can think of that would rattle with the battery pack out, neither one of which should be loose enough to rattle. They are the switch (if it's loose), or the LED (if the blade isn't in all the way).
That's all I can think of. Maybe someone else will have an idea?