What makes these sources not credible in your mind? I have not observed them reporting anything incorrectly. They are citing military experts who know the technical capabilities of these weapons and defense systems. If you want to refute what they say, show how a slower Patriot missile could target and intercept a much faster mach 5 missile. It is basic physics without getting deeply into rocket science.
From the theinteldrop link: "several sources within the Russian military and defense industry told the newspaper Izvestia on Saturday"
From the sputnikglobe link: "Moscow-based military expert Alexey Leonkov told Sputnik"