It's good to read different opinions.
I tried on my XC bike the cooma silver (ex-plus compound) and to me they are pure junk; very low friction, basically not braking even after bedding in.
I was induced by their technical explanation with friction factors etc etc; by the way the ex plus should be the best in the range, I imagine the other compounds.
Then I ordered the ZTTO metallic and they are really good; great bite and stropping power, maybe a little squeaky with wet rotor; I was pretty confident as
normally everything from ZTTO is between quite good and very good.

I am 83 Kg, ok not a fast rider, but the frame after the mod looks stiff enough; about possible future instant catastrophic failures I don't know of course. Anyway the rear triangle is stressed in a "dangerous" way only when sliding side-ward or riding on a berm, quite rare situation, in fact even a big jump or drop should produce an axial and quite symmetric force.
Said that after all what has been written here and the not so cheap rear triangle fix from haideli (300$) and the not so great support if I need to buy a frame today I would avoid this one.

I've a custom AM831 and I've totalized more than 300 km on it, including a couple of bike parks. So it's "only" 300 km but the bike has been well tested.
About the flex issue: the problem was there, even if in my frame probably the bearings weren't pushed out of the recesses so it wasn't that bad; after I made the JJJ brilliant fix the rear is much more stiff, still I don't know if a brand bike is more stiff; I think after the mod the bike is ok.
Generally I love the bike, I assembled it trying to keep it light, it's around 12.6 Kg, a record for a 160/150 mm dual suspension; it pedals uphill very well, also I found very useful the DT swiss rear shock that has three positions: open, pedal and locked; the middle position is fantastic to use uphill.
Downhill it's great, it's very fast on the flow, fiddly to jump as probably all of this modern geometry bikes, they are big like aircraft carriers  .
Problems: to me press fit bottom bracket is a very,very bad idea, especially on a carbon frame;said this the original bottom bracket was almost locked, bearing destroyed from water; anyway I managed to push it out and replace with a shimano XT. I also have quite a lot of pedal strikes this is my fault as I bought 175 mm cranks, 165 , max 170 would be ideal.
The biggest headache came from manitou mezzer fork that wasn't plush on small bumps, now it's 90% solved after I replaced the damper oil with the lightest I could find.
The bike is fun but I don't trust the frame 100%: all carbon parts (even brand ones) can fail, the knockoff probably have a higher failure rate; anybody that see any crack on the frame please report.
I don't have any squeaks from suspension so far.

Hey i have the same issue with my frame i ordered a couple of derrailer hangers to see if the issue gets fixed, seems to be a QA issue

Where have you found compatible different hangers? Can you provide a link?
Thanx

I am wondering if this frame VPP style suggested in another thread has or not the flex problem.... maybe no as the bolts are through hole tightened on both sides.

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Let's not forget that we are buying frames at less than a third of the price of "reputable" brands, from a remote end of the world that does not always have good reputation. Unless we are completely naive, we know that we are gambling. If it's too good to be true, it may well be. I purchased mine with this in mind, and don't expect any warranty. Moreover, there are several manufacturers using the same mold, and not only Haideli is in question. I bought mine from Winow Cycles, and their attitude is no better.

Otherwise, I'm pretty impressed by how the bike rides. The flexing issue does not impact me yet, as long as the press-fit of the bearings holds, but I'm not very heavy and I don't make my bike slide from side to side like cybrsrce.

I 100% agree; the behaviour of Haideli is very chinese, when the problems come to surface they try to avoid direct confrontation. I also didn't expect any warranty, and even if they would offer a real warranty, it could cost over 200$ in shipping and maybe 3 months transit time. I was aware of this when I bought the frame and I knew that a new model (even on reputable brands) brings more problems. I just was hoping they made a carbon copy of Santa Cruz, but it's not the case unfortunately.
I have no big flex yet, and I hope the JJJ fix will sort the problem forever; let's keep the community updated if any other issues come afloat.

At first I didn't pay attention to the flex issue, as my bike and many others here were fine, so I was thinking just about few defective ones.
After reading the great JJJ case study I also realize that the design is flawed and all frames potentially will show the flex issue.
JJJ fix is brilliant, Haideli one much less even if they invested in a new mold for rear triangle, obtaining the same result as JJJ on the upper link and maybe making it even worse on the lower; the triangle is beefier but this isn't necessary a good thing.
For sure the problem has to be solved on all frames, even the non flexing ones like mine: as haideli says carbon fiber is an anisotropic material (the paper sheet explanation); unexpected stress in unexpected direction can cause failure even with relatively low force; I would consider the frame dangerous without locking somehow the bearings in the recess.
The big question is if the old triangle section is strong enough after the bearings will be locked in place.
I am still positive that the fix will work and the bike will be a great bike as it is for now; for sure I don't want to invest 300$ in the new triangle or even worse 1000$ in the new haideli model.
We have to accept that we are beta testers of this frame, it's part of the fun too; just I hope at the end I will have a safe and reliable bike.
I am sure everybody isn't riding much due to winter season, but with the coming spring let's keep the community updated about possible failures or defects that this frame could bring.
Merry X-mas to all 831 team!