I have a 21" Mid. 2011 IMac running 10.13.6. 16 Gigs of ram. I updated to 10.13 several months ago. Two issues have developed in the last few weeks. One is when you start up it boots as it should. When you wake it from sleep it takes about 10 seconds to display the password box. It used to come up right after you touch the trackpad. I can live with this. The second issue is IPhoto does not scroll smoothly. It does a lot of jumping up and down in pictures, albums, and events. I migrated the IPhoto to Photos and I don't much care for Photos. I reistalled High Sierra, updated, and replaced IPhoto in applications and Applications Support and it done do good. Is there any thing I can do to repair the second issue other than a format and a new operating system that there is no guarantee it won't do it again. I have a 4 Terabite Hard drive with about 1 1/2 Terabite taken with pictures and video which takes a considerable amount of time to replace on a new operating system. I really would appreciate some help. Thanks. Jeff.