RSS: Service Unavailable

Have some problems with rss going "offline". Practically it means that my rss feeds are working immediately after I add a new post or update a post. After a while (not sure how long), it goes down and the rss feed says "Service Unavailable". All it takes to get it back is to randomly click update on a post. No conflict with plugins has been detected so I am out of options. All this started after the 4.6.1 update.