Cependant la rémission est suffisante

09:42 Nov 3, 2017 

In the end, I translated the phrase literally - ""However, the remission is sufficient to begin a return to work", or something like that. I told the client about my concerns and she said, "You are absolutely right, there is a mistake in this sentence. Thank you for your diligence and your efficiency." She didn't say anything else though so I suppose she'll fix it herself.

17:46 Oct 31, 2017 

On the subject of it-means-what-it-says, then it might help to consider the meaning of "instaurer" here is not really "to begin", but just simply a slightly more formal way of saying that it can be done. ("It" is going back to work).
However, in light of the fact that this sentence does not fit the rest of the context, thenmakes no sense given the extra context. The sentence itself is easy enough to understand, but unless I am mistaken your clients have not helped you much by saying that there is a mistake if they have not said what the mistake is. Did the client seriously say" Yes, there's a mistake", without saying what he mistake was, or that they would look into it and report back to you? If they simply say, yes, there's a mistake, then I wish you good luck. All you can do is translate it as it is and make sure that you point out the incoherence.

Good luck with it!

In fact, you have "cependant" so I think that it should simply be "insuffisant...".

15:41 Oct 30, 2017 

I just love these questions where one person has all the facts and we are supposed to guess blind. Whatever the mistake, the sentence still means what it says. Perhaps it should read "n'est pas suffisante".
I'm outta here

15:23 Oct 30, 2017 

The client replied just now. She said that there is indeed a mistake the sentence! Aha! I knew it!

Maybe I should have mentioned it in the question, but there were other sentences that made me think the phrase was a mistake:
"Il est prématuré de retourner madame X au travail."
"Les restrictions médicales sont envers tout travail rémunérateur : madame X isa risquerait d'aggraver son anxiété par un retour à ses activités professionnelles à ce moment."

These sentences conflict with phrase "la rémission est suffisante pour instaurer un retour au travail"

13:42 Oct 30, 2017 

and your rationale is not logical in relation to the words that make perfect sense

13:32 Oct 30, 2017 

Hmm... I'm not convinced. I've sent a note to the client about it. If they think it's a problem, they can sort it out.

11:08 Oct 30, 2017 

she is less stressed and has fewer panic attacks. (All is not perfect but) she is well enough to start the process of going back to work (even if her medication needs adjustment)