No one gets "let go" from eJ. Once you're on the line, MPL or fATPL, then you have an interview for your permanent contract after 12-15 months. Thereafter you are a on a permanent contract and will not "let go" unless dismissed for an number of reasons.
I have heard of guys failing the initial flexi-to-perm interview, but they all subsequently passed at the second attempt. Remember during the flexi year you can be dismissed with no notice for any disciplinary reasons, so any one who claims to be have been "let go" will probably be covering something. As with any job though, keep your head down and don't try not to draw attention to yourself!
I also know of one MPL chap who failed his initial line training so he was never released onto the line- this would be classed as a training failure.