Feedbro doesn't really skip any articles but that feed looks like a relatively "high frequency" feed which has lots of entries during the day. For example if at night your computer is off, Feedbro can't scan the feed so if the XML provides only latest 20 entries and during the time off more than 20 new entries are posted, there's a chance to "not see" some articles. You can fix this by selecting "Feedly" to the "Proxy" setting when adding the feed. This will load the feed using Feedly as a proxy that stores all entries 24/7.