This may (or may not) be related to JRA-34812

I have a multi-line text custom field (mitigating actions) applied to all issue types in a project. The project also has another custom drop-down field "Client".

I have a filter set up for this project that displays mitigating actions on-screen, for all clients, and exports to excel (current fields) ok.

However, when I filter the list by "client" (e.g. just show "Client ABC") Mitigating actions is NOT exported (even though it's still visible on screen).