I have got a circline 32 watt FL tube, and after testing it on my setup, I accidentally bumbled it on a cabinet and it makes a rattle.
It still works, and the rattle happens when I turn it a little bit, shake it, or move it much.
I looked at the electrodes under a light, they look fine.
I can't locate where the rattling comes from.
It also happens with my plug in ballast-less CFL.
That happens when it slid a few inches when I accidentally let go of it while putting it in it's package.
Currently, I have no way of testing the CFL.
Should I return the circline tube? Or should I keep it and not worry?
It's urgent!
And it's Ace Hardware brand, Which means GE.

Shake the loose part to the center of the lamp and light through. Probably will be some small glass part that cracked from near the wires coming in. Not too good but i guess won't affect lamp life if its a small piece (big one can open an air leak)

If there is nothing, open the connector maybe its there

Most pin base CFLs have a starter in the base and that is rattling

Shake the loose part to the center of the lamp and light through. Probably will be some small glass part that cracked from near the wires coming in.

What does that mean? I get it if it's a loose thing roaming around in the tube, But this seems to just be in one spot.

I just opened the connector up and saw that it was all ok, nothing bad.
But will opening the connector damage anything? Do I need to test it again? It's a pain to test because I have to get the cord, ballast wires, wire nuts, and take the fixture out of the box. Is it likely OK?
I still hear the rattling.

Update: I found the rattler; It was a small ball of metal caught in a pocket in the glass.
It won't do much harm, but after all of the messing around, I measured the electrode resistance.
It was 2.2 Ohms for each filament, and I will try to forget about this bulb because it's been a really stress causing one. 
I will get another bulb or another one tomorrow.
It looks like some of the leads are almost touching.
Let's forget about this circline lamp now, and pretend it never happened.