So, I know this sounds strange, but hear me out.
คาสิโนสดUFADEALI've been storing some DIMMS (about 15 of them, a mix of DDR and DDR3) for a few years, mostly in the plastic cases they came in. All of these have heatspreaders on them. Most came with them from the plant, but two were added later. All of these DIMMs are now dead, and none of the machines I try them on will work with them. They used to work in the PCs I had that could handle them, but now nothing. All of my DIMMs that don't have heatspreaders and are "naked" are fine. Regularly used PCs (DDR4, with heatspreaders) are fine.
Why might this be happening? What causes heat to expand or contract? Something else?