This somewhat relates to JENKINS-33840
but the problem is that the stages that run in parallel, and/or finish after a failure get marked as "failed"

example pipeline:

stage 'parallel'
def error;
node {
  try {
    parallel(
      b: { stage 'b'; error 'died' },
      c: { stage 'c'; echo 'c' },
      // this branch takes longer than b and c
      a: { stage 'a'; sleep 25; echo'a' },
      failFast: false
    )
  } finally {
    stage 'Cleanup'
    echo "done with all"
  }
}

Expected behavior is that stage 'b' is marked as failure, the build is marked as failure, and all other stages are executed successfully. But as you can see in the screenshot, 'a' and 'Cleanup' are marked as 'failed'

NOTE:

• changing {{b: { stage 'b'; error 'died' }}} to {{b: { stage 'b'; echo 'died' }}}, everything is green
• removing the try/finally, 'Cleanup' is not executed, and 'a' is still marked as 'failed'