This just started happening. I'm a member of a music forum. There is a thread there where people post links to youtube videos. I go to the link. When I want to go back to the forum, I hit the red dot in the upper left hand corner and I'm back. It doesn't do that anymore. I lose Safari. I have to go back to Safari to get back to the forum. The back arrow doesn't help either. This started after I downloaded a Safari software update yesterday.