Probably you went on a forked chain, so rescan don't fix the issue, the only way to recover is to delete the downloaded blockchain and restart from zero or from a snapshot.

You can find an exaustive guide to handle the issue here : https://diamond-info.github.io/#q18

Also explained by shveicar here : https://bitcointalk.org/index.php?topic=580725.msg53474861#msg53474861

and here https://bitcointalk.org/index.php?topic=580725.msg53413293#msg53413293
and here https://bitcointalk.org/index.php?topic=580725.msg48082642#msg48082642

Cheers