This problem has been around for a few years now and when it first appeared it caused quite an uproar in the Intel SSD forums. Intel found a solution to the problem, updated the firmware and provided a download for users. There was only one problem, the firmware upgrade results with a complete overwrite of the drive wiping all traces of data.
The problem is that there are several copies of the translator (FTL) so we need to use the best version in order to recover as much data as possible. Typically there are 4 major versions with 4 sub versions giving a total of 16 combinations. However we are now at a stage where we can recover the vast majority of data in drives that show the BAD_CTX problems.
The problem is also known as Bad Context 13x Error.