I'm working with Adobe CC 2018. Ever since I updated from 2017 to 2018 my saved workspace disappears every time I start a new project. It doesn't just default, it's gone for good. When I re-create a new workspace on that new project, it will stick. It's the new projects that are the problem.
My downloaded presets also disappear...which is probably related. Also, my most recent projects no longer appear when booting up.
I'm running into the similar issue w/ Premiere 2018. I did see on-line advice to "Restore Saved Workspace" (Workspace drop down menu) as a possible fix. I did create extra Workspace templates, so if one went blank I could switch to the other and keep working. Also, I created a new project and ported the Seq into it, and that seemed to straighten things out. So, perhaps we're dealing w/ corrupted Workspace code. I'd love to hear a definitive solution.
I suppose we're privileged to be a part of Adobe's global beta tester program:-)