So just to make a short story long, this customer brought me his PC about 2 months ago. He was having crashes and when he brought me the PC, the ram wasn't configured correctly, the OS was installed on an old mechanical HDD even though he had an SSD, and one or two other issues you would expect to see from a novice PC builder. I sorted all that out and ran furmark for a while since he had said it crashed during games and it didn't crash or have any issues with furmark, so I let him know and he came to pick it up. About 3 weeks later he contacted me and told me it crashed again, so I told him to bring it back. This customer actually lives about an hour away and I'm not really sure why he decided to have me do the service since he could definitely have found someone more local, so he wanted to try some stuff on his own before driving out again. I told him if he brought it back I might end up doing an RMA on the motherboard, so he went ahead and replaced the motherboard himself, as in bought a new one and did not do an RMA, and replaced the PSU.
The new board didn't post at all. He tried a different CPU he pulled out of his friends PC and it didn't work either. The customer at this point has a B550 board and a Ryzen 3600, and his friends CPU that he tried was a 1700X, which of course he did not tell me so I didn't know what CPU he had tested with. (1700X is not supported by B550 even though it's the same socket)
Turned out he had also neglected to hook up an extra 4pin power connector on the mobo, and his PSU was modular so he had to get me the cable. Hooked up the cable, still no post. At this point I decided to ignore the list of thing he told me he had already tried and just started testing everything from scratch. Eventually I swapped his 3600 with the 3600 I have in my second PC and my CPU worked in his PC while his CPU did not work in mine, so finally we knew the CPU was the issue. At the point he brough the PC back it had been a while and he had replaced enough of his parts (against my recommendation) that it was basically a different PC so I would have to charge him again. When we started talking about replacement CPU prices, I suggested he go for a 16 thread CPU instead of the 3600 so it would last throughout the PS5 era. He was interested, and I quoted him some prices on used parts. He then asked me if I could bring the price down so I offered to give him a discount if he gave me the old motherboard he replaced that still works (B450) and the dead 3600 CPU. He gladly agreed and was excited at the offer. I gave him $70 off total for both, and I have already gotten and RMA approval for the 3600 so I will be able to resell both the mobo and CPU for full used resell value, he gets to pay less, and he's taking my 3700X while I swap that out to a 5800X for myself.
I feel kinda bad that he had to bring it back, but if he had been local that would have been a non-issue. Not only that but a bad CPU is usually the most annoying thing to diagnose, and rare to cause issues, so typically I'd try everything else first.
Just thought that was kind-of an interesting rant. If anyone wants a used 3600 or B450 mobo, let me know!