I have a large number of feeds for the same website, and I've noticed a lot of my feeds will fail to update during the automatic update and show the red X (the status message says "Server replied: Not Found!"). I think the problem might be that the server is being overloaded with too many requests in a very short period of time, since QuiteRSS updates each feed very quickly.
Is there a way to put a short delay between each feed during the auto-update process, or at least automatically retry all feeds that failed? Thanks!
unfortunately this is not possible yet.
But you can try to play with the individual update intervals for each feed configurable in the feed properties.