[Mark McLeod]

No "else" is necessary. The last "set" wins.
The code just works out that button 2 wins any tie, and in a tie the solenoid just gets set twice, but so fast that the system won't even notice.

Having both yellow signal lights on means both sides are energized and attempting to pull in opposing directions. So the solenoid shouldn't move from whatever position it is current in.

The yellow solenoid signal lights for each side should only light when they have power and consequential are active, otherwise they don't get power to even light the signal light.
If the solenoid module is showing green for one of the sides (power on), and dark for the opposite side (power off), then the corresponding signal lights should be yellow and dark.
So there seems to be some sort of short sending power to the wrongly lit side of the solenoid.

Either wires are crossed or the solenoid module is powering output pins when it shouldn't be.
Use your meter to verify that power is indeed getting to what should be the unpowered side. Test at the solenoid module pins without the solenoid connected.