The way to get The Defender challenge to progress is to unlock any other challenge after it.
For example I got my 5th defend on Ryloth, stayed in the lobby, and played the next game where I completed a Poe Dameron challenge. (Any challenge should do it.)
For some reason this is the only way to get the challenge to not reset.
I now have all multiplayer challenges completed (besides A Tremendous Service which seems to be bugged as well)
Completing a challenge right after doesn't always work. I did the same thing but with a different challenge and it didn't give it to me.
