One of possible explanations would be that the data are out of range of the Scope block. If in doubt, please use a To Workspace block (or set up the Scope so that it stores its data to workspace) and analyze the data in the workspace. This way, you will be able to see even any infinities or NaNs your model may produce.
And, please try to keep the Duration parameter at a reasonable value. 0.8 seconds at 1e-4 sample time is 8000 samples, so you may want to set Duration to 10000 or maybe, say, even to 50000 to be extra safe, but not to 1e6. The memory for these buffers is real-time accessible non-swappable memory which is quite a precious resource. Overallocating it by such a huge margin only reduces the overall performance and does not help anything.
