A little oddity, but a bug nonetheless
1) Equip and Rail dock a Turret Gun to a base
2) Delete the rail docker that is in use, and replace with a block such as power reactor/capacitor
3) Flip to flight-mode, and look at Weapons menu. The Power Reactor/capacitor will now "occupy" the rail docker slot in the flight mode weapons bar
{F2648}
Have yet to test further, but this has happened all the time with me under those steps to say its reproduce able.