i have years and terabytes of ECC DDR4 and DDR5 memories, UDIMM and RDIMM, with edac enabled all this time, and i have literally never once observed a single error correction. however, (1) i built all these computers myself (2) the servers are located on the middle floor a thick, concrete multi-story warehouse-to-office conversion. as others have said, on a correctly built computer, the source of bit flips is cosmic radiation, and there is a lot of mass between these machines and the sky.