UE 4.15.x editor viewport doesn’t clear viewport properly and leaves artifacts. UE 4.14.3 doesn’t have this problem. See attachments.
Ubuntu 16.10
Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz
GL_VENDOR: Intel Open Source Technology Center
GL_RENDERER: Mesa DRI Intel(R) Kabylake GT2
GL_VERSION: 4.5 (Core Profile) Mesa 17.0.0
GL_SHADING_LANGUAGE_VERSION: 4.50