Sonoff Dual R3 on blind mode keeps one of the relays active when it shouldn't

[JGeek00]

I have my Sonoff Dual R3 configured on this way:
SetOption80 1
ShutterRelay 1
ShutterMode 1
SwitchMode 0

The physical control is a three position switch. It works like this:

• Top position: it sends voltage to the S1 pin
• Middle position: it doesn't send voltage to any pins
• Bottom position: it sends voltage to the S2 pin

This is how it's connected:

I'm doing this:

1. I close the blind with the physical control
2. While it's still closing, open it with the web ui
3. Wait until the blind is completely open
4. Move the physical control to the middle position

Actual result:
When the switch is moved to the middle position, the blind starts closing. It seems that because the first action wasn't completed, because it was overridden by the second action, when the switch is moved to the middle position, for some reason it recovers the unfinished first action. That shouldn't happen. When the second action is executed, it should override completely the first one, and the first action should never be executed.

Expected result:
The blind should not move from the open position