Javascript redirection stalled and F5 reload

I have a behaviour on production site which cannot reproduce locally. Is it possible this behaviour in some browsers?
I have two pages A.php and B.php. I execute A.php, which redirects via Javascript to B.php, after making some php processing. Is it possible that if there is a lot of traffic, and B is no loaded, and still not showing on the URL bar, if I hit F5, I load A.php again, making some processing, but the redirection of the first step is still in process so:

  1. A.php is executed
  2. document.location href and load of B.php is started but stalled.
  3. F5 makes A.php executed again (this time without document.location.href as there is no stream data sent back to the browser yet)
  4. The 2) step is resumed when some stream data is sent from B.php

This would make that a F5 of impatient users would load A two times. Is it possible? I tried to reproduce it, putting a session variable to not write document.location.href a second time, but all I get is 1), 2) (I put a sleep() to reproduce), 3) F5 again loads A, without the redirect, and of course, it never redirects, it never reaches step 4).