The Isis Adventure

I recently bought my first Isis. The Titanium version from marbles in USA.
I think I've had it to the halfway point a few times though I can't be sure. The plunger has solidly stopped short, but there is definitely something larger than the other two bearings moving around in there.
I hear the bearings making a light *swish, swish* sound in the puzzle but there is also a heaver *clack-clack* sound when I shake it. I've read that some puzzles have had a key inside in the past that caused some issues. I'm worried something may have come loose and is causing problems.

Any help would be appreciated.

Sounds like everything is okay. You're most likely hearing the key that comes inside the marbles edition. It's noticeably more rattly than the bearings. Having opened my marbles Isis many times, there shouldn't be anything that can move around other than what's been mentioned here already.

Brian706 - Thank you for the quick reply.
Your confidence is inspiring though I'm still worried that something might be getting in the way of the other two bearings after I get to the halfway point.
Prior to the halfway point I can audibly make out a distinct *swish swish* of them rolling around. After that, with the plunger 1/2 depressed, all I hear is the *clack-clack* or *tink-tink* of what sounds like a hinged, or sliding, bit of metal rocking back and forth as I rotate the Puzzle gently or shake it vigorously.
I can't hear them rolling or bouncing around at all after the plunger is bottomed out at halfway, inverted or not.

I agree, it's probably the key. Mine does the same thing, and I was surprised that there was a physical key inside of mine when I got it open. I heard they were no longer putting keys in them. Mine is the titanium blue version from marbles.

Okay, based on your description you are definitely hearing the key at the halfway point, and in no way will the key hinder your progress. You will understand once you can see the internals of your puzzle. I know the reason you are not hearing the ball bearings at the halfway point and it's because of something you are doing (or rather not doing?)... I don't want to spoil your adventure, so that's all I'm going to say.

Please be confident that your puzzle is in working order and that you just have a little bit more to work out! If you have a specific question about your progress at the half way point, feel free to shoot me a PM as to not reveal anything major in the open forums. I won't give you any spoilers but I can try to give a gentle nudge if you need it.

SOLVED!
Thanks all for the encouragement. I was getting pretty concerned about it.
Now that I see where the key is placed, I know there was no way it could've interfered with the process.

I've had my eye on these since 2007 and was excited to finally splurge a little and get one of my own. I was worried my luck had handed me a faulty orb. All is well!
Now to move on to the puzzle box Hmmm... this one is proving much more difficult to decipher.

Hey congrats!!! Also, I don't think anyone has solved the puzzle box, but I could be wrong about that.

Also, now that you've seen the inside of the puzzle, do you understand why you weren't hearing the ball bearings?

Congrats!!! Glad to help. That first time unlocking it can be tricky, but like Brian706 said, once you see the inner workings, you will definitely be able to understand it better.