Paint "transparent" selection works incorrectly

Scenario 1:

1. Draw any image in the Paint
2. Choise "Selection tool"
3. Switch to "transparent" mode (lowest button on left toolbar)
4. Select any area
5. Drag the selected piece

Result: unexpected vertical lines, unexpected  new colors

Scenario 2:

1. Draw any image in the Paint
2. Choise "Selection tool"
3. Switch to "transparent" mode (lowest button on left toolbar)
4. Set background color (2nd color on the palette) to non white color
5. Select any area
6. Drag the selected piece

Result: unexpected new colors

Please note: the second scenario is reproducible on Windows too (a little differently) (If run Reactos Paint on Windows)