It is properly greased.
There are loose or missing pins in the slide mechanism of sliding 5th wheel.
Make sure locking pins are fully engaged.
All of the above.
Red ; blue
Blue ; red
Orange ; green
Green ; blue
That the landing gear is in the upright position.
The trailer brakes are on.
Your air brakes are off.
The tractor protection valve is normal.
Often do not have spring brakes.
Usually need a glad hand converter.
Are illegal in all 50 states.
When the fifth wheel is not secured properly.
Taking an unfamiliar route.
The path of your steer wheels vs. the trailer wheels.
Possum-belly livestock trailers.
Dry box van trailers.
Reefer (refrigerated) trailers.
Here's an interesting quiz for you.