This is a bug about the connection of hinge rotator, which is when you put the two hinge rotators on a fuselage, and connect one of the two rotators to second fuselage, and then use shift+k to make another rotator that has not connected the second fuselage to connect the second fuselage, one of the two rotators won‘t work.

To understand this bug better, I use three methods to demonstrate it.

The first is that use a fuselage to connect with two hinge rotators (green and blue, I use shift+k to connect the blue rotator to the fuselage), you can see this bug

The second method is that use TWO fuselages to connect TWO rotators, and no problem here.

The third method is that connect a red fuselage to the green rotator,and connect yellow fuselage to red fuselage, and finally, use shift+K to connect the blue rotator to the yellow fuselage, the rotator did not work.

https://www.simpleplanes.com/a/xd096d/BUG