It's not uncommon in development to have a bug that is caused by something downstream. Replying 'not my bug' is fine internally but bad professionally because it's still on you to find a workaround - upstream (users, customers) don't give a flying f..k who's bug it is. So I'd put at least partly on Signal here for not implementing a (temporary, we hope) workaround and reporting the bug to google. Also VM for having inadequate testing. I bet they loaded it on iOS and called it good..