Thanks Kern and Wanderlei,
I've tried bls and I get:
06-Jul 11:48 bls JobId 0: Error: block.c:429 Read error on fd=3 at file:blk 0:397845547 on device "WStorage2" (/backup/external/2week). ERR=Input/output error.
06-Jul 11:48 bls JobId 0: Error: read_records.c:124 block.c:429 Read error on fd=3 at file:blk 0:397845547 on device "WStorage2" (/backup/external/2week). ERR=Input/output error.