Roto brush's boundary not visible with hand tool

When I use the roto brush, if I switch a hand tool or move the view by middle mouse button, background disappears.

Here's the correct view, but if I switch to hand tool, or press and hold the middle mouse button and move the mouse,

suddenly brings this view. To back to correct view, I have to zoom in/out to refresh the view.

I think there is a bug in the code of refreshing the view.

Is there any solution? Or I have to wait for next update?

--- Some updates ---

There seems to have multiple ways to back to normal view, for example

- Press alt (switch to "minus" tool)

- Move mouse cursor to outside of the viewer screen

- Zoom in/out

Win 10 Pro 64bit

i7-8700K

16GB memory

Geforce GTX 1080Ti (Latest stable driver)