Changed Rotors/Pads and now a rattle??!

[Polyal]

OMG this is now driving me nuts! A little backgorund.

After getting my TE I got all new Rotors and Pads installed, I generally do this with most cars I buy, anyway..the reason for the refresh was the old sets were squealing.

So I ordered some slotted/drilled DBA rotors and some RESMA pads through the forum. Worked great, good feel, but my god the amount of dust they made was a joke and within one week they somehow glazed the rotors. Great, so I had to get the rotors machined (now 2 weeks old!) and told them to through the pads in the bin.

So I ok'd them to pick some pads that had bite, not much dust, and were quiet. They installed some bendix Stealth pads.

These work very well and solve all the above problems. Until a week later I start to get this god awful rattling from the front end..sounds like its about to fall apart.

It only happens when the brakes are not applied, which is alot of the time! So I take it back to the shop and say WTF, that wasnt happening before. They call me up and say all fixed, we had to shim the pads...stupid me was happy with that, noise gone.

So here we are a few weeks later and its rattling again! I CBF'd taking it back to that shop as I am working in the opposite direction now.

So before going to another place can anyone explain to me why something is loose in the first place and why pads or any brake parts would ever need shimming?