Async Task not returning results

I have around 10-15 ecto queries which I want to run async in my API code.
I am using Task.async and Task.yeild_many

Following is the code for async task -

def get_tasks() do
  task_1 =
      Task.async(SomeModule, :some_function, [
          param_1,
          param_2
      ])

  task_2 =
      Task.async(SomeModule, :some_function, [
          param_1,
          param_2
      ])

  task_3 =
      Task.async(SomeModule, :some_function, [
          param_1,
          param_2
      ])

  [task_1, task_2, task_3]
end

I get the tasks in my main function as -

        [
          {_, task_1},
          {_, task_2},
          {_, task_3}
        ] =
          [
            task_1,
            task_2,
            task_3,
          ]
          |> MyCode.TaskHelper.yeild_multiple_tasks()

And my task helper code is given below -

defmodule MyCode.TaskHelper do

  def get_results_or_shutdown(tasks_with_results) do
    Enum.map(tasks_with_results, fn {task, res} ->
      res || Task.shutdown(task, :brutal_kill)
    end)
  end

  @doc """
  Returns the result of multiple tasks ran parallely

  ## Parameters
    - task_list: list, a list of all tasks
  """
  def yeild_multiple_tasks(task_list) do
    task_list
    |> Task.yield_many()
    |> get_results_or_shutdown()
  end
end

Each tasks are ecto queries.
The issue is the tasks are behaving randomly. Sometimes they return results, sometimes they don’t. But there was no time when all the tasks have return results (for the representational purpose I have written 3 tasks,
but I have around 10-15 async tasks).
I ran the code synchronously, and it returned the correct results (obviously). I tried changing the pool_size in config to 50 for Repo, but to no avail.

Can someone please help me out with this? I am quite stuck here.