Unable to claim reward although I've completed the milestone

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)