I am simply relaying what I have read from experienced FIX programmers who, having put up with these problems, invented the DTC protocol in the first place.

On a side note, I wrote the Ally Plugin, which used a small number of FIX messages in a special XML format called FIXML, jumbled with their own proprietary REST stuff. And none of the FIXML messages were actually compliant with the official FIXML schema! Ally ignored me when I asked about it.

But that was a mixed interface. Hopefully I won’t have such hiccups working with pure FIX. None!