Because I'm an Evernote Plus subscriber, I did submit a ticket (# 1274695). Basically, Evernote was never able to recreate the problem. However, I had the problem on two different macbook pros, one of which was running Yosemite 10.10.5, and the other running El Capitan 10.11. The problem only occurred using Safari, not in Chrome or Firefox. It appeared to me the problem was caused by activating the web clipper before some feature (or ad) on the web page was fully loaded. By refreshing and waiting to make sure the entire page was loaded, the problem would not occur.