Mydisktest V2.42 [better] Access

You have a "fake" drive. The software found that after a certain point (e.g., 16GB), the data disappeared or became corrupted, proving the 1TB label is a lie. The Technical Side: How "Expansion" Works

: Runs continuous cycles to stress-test the longevity and reliability of the storage medium . Mydisktest V2.42

Are you a specific USB drive or SD card? You have a "fake" drive