I Have NVS2500, It has worked well till recently

When downloading large amounts continuously it gets hot.
Then the footage does not copy correctly from the SXS cards even though it has done a complete 'verify'. I find this out when transferring to the computer(Mac) It says it can't find the contents of the file. Only on one or 2 files.
The files are corrupted.
So I re transfer from cards. With no problem when cooler.

The self test says may have errors please check it again at PC. It has always said this from new.
Should I buy a new drive? Or is is something else? The problem is I can't be sure of a safe copy until I have a transfer to a computer, which defeats the purpose somewhat
Help