Steps to reproduce:
1. Create a new "Universal 2D" project
2. Open Windows -> 2D -> Tile Palette
3. Click the "Create New Tile Palette" dropdown button and select the first entry
4. Click the "Create" button
5. Select any Folder in the OS window
6. Select any texture and drag it to the area with the label: "Drag Tile, Sprite or Texture (Sprite type) asset/s here."
7. Click "Save" in the OS pop-up window
8. Select the imported texture by clicking on it
9. Select the brush tool "Paint a filled box with active brush."
10. In the Scene window, draw a rectangle by clicking the left mouse button in one spot, then dragging the cursor a bit and releasing the left mouse button
11. Observe that painted tiles are visible at first, and you need to mouse over each tile for them to be visible, or redo the previous step twice

Actual results: Painted cells are not immediately visible, and you have to repeat the action or mouse over each cell for it to appear.

Expected results: All the cells in the Scene Window should be painted and immediately visible.

Reproducible with versions:  6000.4.0a2, 6000.4.0b5, 6000.5.0a5

Not reproducible with versions:  6000.3.4f1, 6000.4.0a1

Tested on (OS):  Windows, MacOS