What level of intelligence you need to replace thermal paste in GPU I do not know but as sure as hell know that thermal pads do not require thermal paste. And even if by a little margin this mistake is visible then there might be more mistakes you might have done while repasting which at first glance would not be visible.
GPU primarily needs the thermal on it, next the VRAMs, if the gpu is opened up, and if by any chance the thermal pads are too tightly stuck on both the heatsink and the VRAM, opening the gpu will cause the thermal pads to spread apart and tear down into halves. In such a case, if kept back as they are right now, it will only cause a gap between both the halves, resulting in poor conductivity of the heat.
Adding a little bit of thermal paste can help fill those gaps, resulting in proper functioning of the thermal pads.
Looks like @TechnologyHell has not logged in after last Tuesday. He is probably reading this thread as a Guest and don't think he is looking to help the buyer anymore in getting the GPU repaired or returning at least 50% of the amount to the buyer. He is as good as gone. Hopefully he will stay away from TE and nobody in future will deal with him from here anymore.
Not everyone like you is free all day to look up the forum every moment. People are often stuck with workloads, and get held at situations where they barely spare time to sleep well.
Rest for all others, I am still willing to help out the customer in recovering the card back up, but the type of response from the community and the opinions from vendors and other sellers tells me that I should give it up and leave the matter as it is.
1. This primarily looks like a short on a capacitor, and since you have already opened the card up, pls have a look at the 8+8pin power connectors if you see any rectangular capacitor to be blackened, or look different from others. This same could also be visible near the smaller part of the PCI port (one long part and one small part, the smaller one is for the on board power). It can be both, a short on the capacitor, capacitor malfunction, or oxidation which is causing the terminals of the cap to be connected via moisture / grime.
2. The other pc that you tested this card on, pls mention the psu specs, just wanna cross check upon the power demands and supplies. This is a very basic level card, cant' handle slightest fluctuations, even a little bit of voltage fluctuation can cause any minute component to short / blow up, causing an overall short on the power rail of the card.
I am up for two resolutions.
1 - Partial pay back and take the card returned.
2 - Pay for the repairing charges and get the card back to the customer.
But before any of these are accepted, I need a clear cut confirmation regarding the issue with the card.
What I know that I have given a working card, and if it has died in the hands of the customer, I believe it is not at my fault anymore. Still if I am here, responding back, offering resolutions, I expect the unemployed people on the form to kindly maintain their language used publicly, and rather to be polite in discussions.
Note : If I wanna scam, I can just easily leave this forum, mark it as spam on my mail, block the customer, and disappear forever. Just for your kind information, thought you didnt' have got good scams on your past, so gave you a clue. I've been through many, not a single one of them responded back after I made the payment.