Question AIO Cooling system rarely starts to roar and rattle

[SilverChad]

Hi, My system age is 4 month, in this 4 month this happened 2 times, first 1 month ago and second today.
When my pc is on sleep or shuttled down and I turn it on the fans of AIO which are at top of the case, start to roar, first time was the 1/3 fan and today it was 3/3 fan.
If i hit the fan hard sound gets lower but doesn't go away, if I turn off or sleep pc for 5 minute and turn it on back rattle noise goes away.

I attached a sound sample of rattle, Is this a serious issue?
It's a high-end pc and cooler is MasterLiquid ML360 Illusion CPU Liquid Cooler

Sound of rattle :
https://drive.google.com/file/d/11uOQKvjn1naAMo0HRIYmZAOauHOr3zpK/view?usp=sharing

 

[scout_03]

look like the blade are touching something coulrdyou remove fans the upper cooler outside the case leaving pump on a for a test .

 

[SilverChad]

look like the blade are touching something coulrdyou remove fans the upper cooler outside the case leaving pump on a for a test .

It happens very rarely for now, and if I want to test it I have to turn it off which fix the problem, I'm confused.

 

[scout_03]

take a magnifier system off and if there it not something that touch any fan blade you could also touch then and see if there a sound when you spin it with your finger system off power .