And the comments of the arbitrators should, of course, be translated to the native language of the project, unless it is clear that there is no such need.
Where possible, that would be good. That is just translation into one language (or maybe a couple of it's a dispute that crosses into two projects), rather than translation into every language represented on the committee, and doesn't have to be done in real time, it can be done at the end. Real time translation slows down discussion, translation after everything is over is much more practical.