My mind is blown. I took the brush out and no more clicking, put some tape on (round part), put the brush back and no more clicking. THANK YOU
This is just crazy, I’ve lived with that clicking for 3 months. I’ve done deep cleans and taken sober of the casing off and cleaned. My next step was to really take it apart.
August, 2020 - We own Eufy 15C Max. Had same issue. Called Eufy support. They suggested to remove the long roller (that we clean everyday) and run Eufy without it. If the sound is gone, just replace the brush. (It was gone for us - a new roller FIXED it). Support guy said we typically need to replace the Roller Brush every 6 months. (By the way, if that did not fix it, then he said there is something stuck in the internal motor - I have no idea what fixing that would involve.) Anyway, if you already tried what fixed it for us, then call Eufy support (800 number on back of device) - they were very helpful.
Thank you a lot!!! It works!!
Muchas gracias!!!
De nada! 
For my Eufy 11S it was clogged up roller bearing. I took the cap off with pliers and cleaned out an insane amount of hair wrapped up in there (2 dog household). I did pry the bearing out from the roller just a bit.
ja this wheel really should spin freely!
Easy fix for this. Throw it away and buy another brand. I called Eufy for the extremely loud rattle and they offered me a discount on a new vacuum. No Thanks. I’m not going to buy a new vacuum every other year when it fails. It was out of warranty. The plastic piece that holds the roller seems to be the issue. Eufy told me that the engineers would not fix the problem because everyone would want a new vacuum. I started shopping for a Roomba. They’re a lot more expensive but the money saved on constantly buying new vacuums will help. My Eufy doorbell works well so far but it will be hard to recommend any of their products going forward.
My “old Willy” 11S is now doing his heavy job since more than 2 years.
But I do care about him -> cleaning properly!
Enough said!
After cleaning everything else and rattling noise continued, this was the ultimate fix for me. No need for duct tape. Thanks for posting with a picture. Have 2 cats and yes, it was amazing how much hair was under this cap which kept the roller from turning smoothly on bare floor. Now operation is quiet again.
Great you got that fixed.
Hair is poison for the vacs.
Winding!
Enjoy the weekend!
My Eufie became very noisy and this is how I fixed it. Pull out the large roller brush. Take a sharp knife so you are able to pry off the round roller at the opposite end of the square drive end. This is the smaller roller at the very end. It will slide out and you will probably find that it is full of wound up hair. Clean out the hair and reinsert the steel peg and it should be quiet again. Tim
Thanks to everyone who suggested wrapping tape around the square end of the brush, it worked for me! Have ordered a replacement but this will do in the meantime.
THANK YOU for this. I just did the same and yanked out a gross amount of hair and it’s SO MUCH quieter! Your picture really helped.
Yes. I found the same problem and the same reason.
I had the same problem with my 15C. It ran perfectly fine and quiet for two years. All of a sudden it became very noisy. I noticed that he noise seemed to be coming from one of the side brushes. After further inspection, I noticed that one of the side brushes seemed to spin freely while another had some smooth resistance through the gearing. I spoke to the factory and when I explained my findings, they advised me that the motor should not spin freely and that the gears in the side brush motor were likely stripped. Since it was out of warranty, they offered me a 40% discount on select new units. Upon further investigation, I found the side brush motor offered as an accessory on their website. The unit is currently “sold out” which tells me that this is a common problem. I found a new replacement motor on eBay for $26 and installed it yesterday. My RoboVac is back to normal quiet operation! It’s a fairly simple repair and Eufy even has a on instructional video online. Hope this helps someone.
I will do that surgery at my old Willy (ca 3 years old now ) soon.
He agreed and the monkey engineers will help.
They are watching the instruction video daily and told me they are really ready for such a swapping😂
I did the same with “old Willy” left side brush motor.
Will be a three years old robot in June.
There is the possibility to buy spare parts at the EUFY website.
If there is a scratching nose it coulde be caused by the middle brush.
Remove it and listen if its gone after.
If so you could tape the wheel at the right side.
All is fine after. 
Hi there, I’ve found a good long lasting easy solution for the problem, for all you who don’t like tape. The main cause of the problem is that the bearing gets stuck by the hair underneath. The cap what is thought to remain still is carried with the bearing, starting to rotate and grind down the bearing cap holder, everything gets play and that is rattling you hear. So at first it is necessary to remove the hair. You have to pull off the cap with pliers and pull the bearing out. The axis will easily come out. Then it’s easy to remove the hair underneath. Cut a soft sealing ring in half and press it in the slot behind the bearing. It will hold by pressure and won’t fall out if you clean the brush. The cap gets pressure by the holder again and the rattling is gone. If you clean the bearing from time to time everything will be fine.
