I upgraded from Alpha 19 to Alpha 21 and now the scene view camera in my project down at about 20-30fps I would estimate, when it was smooth 60+ before. This persists even if I disable all the content in the scene and is independent of the size of the scene window, settings for the scene camera, gizmos enabled/disabled etc - nothing I tried has improved the framerate. The frame rate in game view after hitting play is unaffected at 120+ fps I tried loading another project and didn't have this issue but that is a much simpler project During the upgrade of my project to alpha 21 it stalled on importing the 'defaul't layout file for a long time (like 5 minutes+). I remember this happened previously when upgrading to alpha 15 from alpha 13. Then this time my system hard locked up when the Editor was loading at "execute menus" or something like that (but it loaded fine after restarting). I'm going to try deleting my project and reupgrading it from backup and will report back.