Thanks for the post @98929873!
This is actually not a bug, but an intended change to Lifeline back at the beginning of the Legacy Update.
I've included the relevant part of the patch notes below, but you can see the full list here if you'd like!
- Combat Revive: No longer deploys a shield. Can now revive two players at the same time. Can now cancel active revives in progress to allow your teammate to defend themselves with their knockdown shield.