Overtightening heatsink?
Its like that but way too sensitive. I've deliberately been gentle and it will still fail especially if I set it upright with fans on the heatsink.
Can you take some pictures? You probably bent something in the socket, or broke a trace. When it flexes just right, it makes the connection.

I think the overtightened heatsink theory is correct. I got it for an LGA1155 motherboard and it needed an adaptor for AM4 which has no safety springs so you can just keep tightening it with no indication of what's too tight.
There's also some sort of dirt on the center left edge that I cleaned out after taking this. I just used isopropyl and a softened (used) toothbrush. After doing that I got a channel of memory back. There's three sticks in the pic because I was trying to determine which channel was bad.
Update: Wow cleaning that bit of gunk really made a difference. I'm back to using the original Ryzen 5700. Really weird that it wasn't an issue in the old build.
Buildapc