Vengeance LPX 3200mhz woes...

Hey everyone, first post here hoping for some advice.

Right at the end of November I hit a couple computer fairs and picked up a load of new components to build a modest Ryzen based system, mainly for image and video editing as my ageing Xeon workstation was getting a bit long in the tooth.

I picked up a 32GB kit of Vengeance LPX 3200mhz for my system and after assembling and seeing up all was running well :)

I noticed in the Cyber Monday sales Amazon had a good deal on the same 32GB kits so decided to pick up another one to max out my ASUS Prime B450+ board with it's maximum listed 64GB of DDR4 3200.

My system was stable for a few days all at stock speeds (I'm not an overclocker as I need stability over speed) but slowly I started having a number of random system freezes, notably when working on very large photoshop files or moving around complex scenes in 3DS Max.

Eventually the system refused to boot whatsoever, powered on to black screen only.

So by process of elimination I found that one of the RAM sticks when removed allowed to the system to boot and run flawlessly every time with the other 3 sticks, even under load.

Putting the suspect stick back in now always results in a no-boot.

Now my problem is two fold...

Firstly is this likely to be a bad stick from the start, or has some kind of incompatibility killed it?

The two RAM kits are identical spec and the correct spec for my board, and as mentioned have not been run beyond their stock speed.

Secondly, I currently have no way of telling which sticks I got from the trader at the computer market and which ones were from Amazon, I'm struggling to find the original receipt for the former, where would this leave me as concerns warranty?

Obviously I have a record on my Amazon account for the other kit, but I'm unsure which kit the possibly defective stick was from :sigh!:

Any help/advice greatly appreciated.

Mick.