I have been having a number of problems with Safari 11 (I'm running Mac OS 10.12.6). There are a lot of weird things, such as being unable to go full screen on youtube, downloading files that won't open (but will download properly in Chrome), items on pages that don't work (or work properly), plus lots of little delays and hangs. My work around is to go to Chrome, which handles all of these things perfectly. Any ideas as to what the problem may be?