I've tested the memory using MemTest, and it's showing errors.
There are four K3KL9L90CM-MGCT chips installed. According to the datasheet, these are LPDDR5X 64Gb modules. However, MemTest is identifying them as LPDDR5 ECC. I don't have much experience with faulty ECC memory, but I know that ECC configurations typically include an additional chip, at least in the server setups I've seen.
I'm not yet sure whether MemTest is correctly detecting ECC in this case. What I do know is that the latest version of MemTest supports DDR2 / DDR3 / (LP)DDR4 / (LP)DDR5(x)...