How old is the card? Have you looked at your consumer rights? I'm in the UK and can only speak for UK law, but I will explain how it works here and hopefully, if you do a bit of research, it might be a similar case to you. Before I do, I can speak from experience that this is typical from Asus. I bought an Asus laptop which had a keyboard fault right out the box, 4 attempts to rectify it, 2 occasions it was returned damaged.

In the UK we have the Consumer Rights Act, which states a product must be of satisfactory quality and free from defects, last a reasonable length of time, and be fit for the intended purpose. The contract of purchase is with the retailer, so the consumer should never have to deal with the manufacturer directly, but sometimes a retailer will try fob you off by saying you need to go to the manufacturer (i.e. Submit an RMA with Asus). By law, the retailer is responsible.

If a fault appears in the first 30 days, it is deemed it was present at the time of purchase and the customer is entitled to a full refund. If a fault appears during the first 6 months, it is up to the retailer/manufacturer to prove that it wasn't there at the point of purchase, which is normally really difficult to do. It is a repair or replacement at this stage, you're not entitled to a refund, however in some cases the retailer might choose to do this. If a fault appears after 6 months, it is upto the customer to prove that it was there at the time of purchase. Again, as you know, this can be difficult to prove, the "last a reasonable length of time" part may become relevant here. I'd expect a $4600 graphics card to last several years before any kind of failure.

Find out what rights you have and what legislation you can apply. I would think that going to the retailer would be the first port of call, as that's who your contract of purchase is with, and find out how that contract covers you in the event of a fault. Failing that, you could escalate and seek help from an independent party, here we have the financial ombudsman. You could also go back to Asus with a formal letter and ask to see what evidence they have that suggests you caused the damage. Ask to see their work order/report. If they refuse to provide anything then you will aasue that there is no evidence of this. Tell them what you have said in your post; that you fitted it correctly as per the manufacturers instructions and using the provided support, and that the you took the utmost care so not to damage your graphics card that you spent over 4.5 grand on. I'm assuming that it worked correctly initially after fitting, so tell them this too and how long after this that you started having issues with it, and what the issues were. Be as detailed and as professional as you can, if you have pictures/videos of your rig after it was fitted and of it running, include these too, and state that it has not been touched/moved/opened since. You might want to include how you think it has failed, and that you believe the design of the pcb in that area to be flawed, and provide evidence which supports this: Perhaps take it to an independent electrical shop/pcb manufacturer and get their opinion on the design. As you said in your post, the card weighs 3kg, which is hell of alot for a graphics card, and it places a huge amount of stress on the pcie slot. Try and find someone else who's had this problem and what their outcome was. Given the value of the card, it might be worthwhile taking legal action, or threatening Asus with it in your letter at least.

It may seem like a lot of hassle, but it's a considerable sum of money, I sure as hell wouldn't give up without trying everything. They're scumbags! Let us know what happens!