Aubeline Brandamir 

The ideal case would be if you could send the file in question to somebody to have a look at, but I understand this is not always possible.

One workaround might be for the client to go back to his INDD file (the original InDesign file format), Export all stories to InCopy and then use the generated ICML files to work with. No guarantee this will work, but it might.

I am sure RWS would be very interested in looking into this as they generally keep their IDML file type in very good shape. Lydia Simplicio 

Daniel

Hello Daniel,

Thank you for your swift feedback!

I'd be happy to share the file should anyone be willing to look into it.

As for the client, they don't seem to be able to help.

Aubeline

Aubeline Brandamir send it over

Hello Lydia,

Thank you!

I have sent you the source (EN) and the target (FR) idmls via a link as a private message.

Aubeline Brandamir while I dont have Adobe I asked support to confirm their experience opening target document provided.
They could with ease apart from some characters looked odd but that is because they dont have all the fonts installed.

To confirm they used:

Hello Lydia Simplicio ,

you mean they could open both the EN and FR idmls without any issue?

If so, it is very strange as none of the conversion tools I used (I don't have InDesign either) worked

Aubeline Brandamir correct no issues opening source or target in native InDesign 

Noted, thanks for confirming.

I'll get back to my client then!