Jerky transition when switching region from fixed sky to a day cycle

1. Open REGION/ESTATE floater, switch to Envirionment tab.
2. Switch the region to using a fixed sky.
3. Choose a visually different day cycle and press Apply button.

Observe: Sometimes, while the new settings are being applied, previous settings become visible for a moment.
Expected: No significant visible changes should occur after pressing the Apply button.

The only exception is day time, which may change due to switching from fixed sky to a day cycle driven by estate time. In other words, sun may move to a new position, which affects lighting.