Update
I have now tested with 40 different rss-feeds on 3.8.3 and 3.9 and the results are the same.
All works 100 % on 3.8.3 (feed to post and shortcode) but switching to 3.9 SHORTCODE works 100 % but FEED TO POST does not.
I have tested on different servers, contacted tech-people on 3 different host where one is a friend of mine and he has tested at HOST-END and get the same result as i do.
As told before i have also set up to new subdomains, one with 3.9 and one with 3.8.3 and the results are as above.
Allen, don’t get me wrong but since more users report this issue i doubt it’s related to feeds, correct me if i’m wrong. Remember, SHORTCODE works, FEED TO POST does not.
Keep up the good work!