True Image 2013 backup errors

Dear trendmicro staff and forum users,
We are experiencing backup errors with acronis true image 2013.
It is configured to make a backup of the C partition to an external USB hard drive.
At about 93 % it always throws an error that it is unable to read a specific sector from the source drive, however the sector ID is always a different one.

We have scanned both hard drives both internally in the computer and externally on another computer with multiple scanning software (HDD regenerator, manufacturer test, onboard diagnostics tests (imac), ...) and no issues where detected, so it seems like the HDD's are ok (i trust that specialized disk software is beter at detecting faulty sectors then acronis).

So this leaves me to think that there is a problem with the program, and not with the HDD.
So the question is, has anyone heard of any simular issues? or does anyone has any suggestions as to solve it?

Acronis true image is installad on an imac 27" (i7) with windows 7 in bootcamp.

I would also like to ad that i don't think it's nice that you allow subscriptions of older, no longer supported products (like this one), to be prolongued under charge witouth any active notification of it not being supported anymore.

Kind regards