I’m making two scenes. The first one is just Suzanne and the camera. In the second run Sequencer and it create a strip with a scene with Susannah.
When playing the sequencer, I observe an extremely low FPS equal to 5.
It can’t be that way. The same situation in 2.79 produces more than 30 FPS.
In the N-pane of the preview the window becomes black when Wireframe is selected. There are no objects.
The Solid mode preview shows flat objects as if they were two-dimensional.
I have poor English, so I recorded video for clarity: