Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors
Your SMART Current Pending Sector has value 1. This means that there is a bad sector on the disk and the drive firmware is unable to reallocate it, but you still have zero reallocated sectors count so it probably recoverable even though your drive have been running for 5 years in not very healthy environment - temperatures are up to 72 C°.
You can try finding this bad sector with
dd if=/dev/sda of=/dev/null and then you'll need to remap this sector by overwriting it.