Cannot release during campaign while in party not in boss fight

Been playing with a party of three, still in campaign, but when we die, we cannot release / respawn at checkpoint. The button is there along side spectate in a nice new UI but its gray. We can not respawn and have to wait for one of the other party members to rez us.

This is changed behavior from prior versions of the game and only happened during boss fights prior. Now it seems to be happening in campaign in general.

Is this intentional?

Logically, yes, it should work that way to prevent killing the boss by throwing bodies at it.
At least that how it worked before.