Looks like there may be a similar issue to #14340 still. When it's still failing, the click for the checkbox is not in the normal position suggesting the element could be moving during page load.

On a failed test:

  cookies=[{:name=>"test_user", :domain=>"127.0.0.1", :value=>"secret_admin", :expires=>nil, :path=>"/", :secure=>false, :httponly=>false}]
  updating counter on page load
    counter page load... finished
  click19={"position"=>{"x"=>80.5, "y"=>208.5}}

(Lines 2/3 show the host_checkbox function that runs on page load succeeded, and line 4 shows the clicking by Poltergeist of the select all checkbox.)

A successful run clicks differently:

  cookies=[{:name=>"test_user", :domain=>"127.0.0.1", :value=>"secret_admin", :expires=>nil, :path=>"/", :secure=>false, :httponly=>false}]
    updating counter on page load
counter page load... finished
  toggleCheck()
    toggleCheck(): checking host_ids_1 to true
  toggleCheck()... finished
  click13={"position"=>{"x"=>80.5, "y"=>197.5}}