Dell OptiPlex 7010 SFF persistent fan rattle after three different heatsinks!

I work for a department that has recently bought over 40 new dell machines to replace a fleet of old optiplex G620's which have to be fair been bullet proof if a little slow.

When looking at the 7010's after we had them delivered I didn't particularly like the small heatisnk and blower assembly but as it is a SFF machine that was to be expected.

The problem is one one machine I cannot get rid of this rattle:

 

This happened with the heatsink this particular machine was first shipped with. Dell support sent a new heatsink out the next day. Super. I fitted it but within 10 minutes it was the same.

Then dell support sent a engineer out to replace it again  and within a week it is again doing as shown in the video above. 

Now I am concerned (I pushed for Dell built machines) that we have a fleet of 40 machines with these seemingly very very low quality fans attached to i7 based workstations and I have serious doubts they will last 7 years like the G620's before them!

Has anyone got any ideas what would be the next port of call? Not particularly happy with just swapping out cheap Chinese fan for cheap Chinese fan over and over again.