How about if I address looking at it from the aspect that the athlete needs to have courage to perform the back skills for the first few times? By definition, Courage is the ability and willingness to confront fear, pain, danger, uncertainty, or intimidation.
If you, the coach, see that the skill and technique are good to perform the skill then rationally it is not dangerous. But in this case, the athlete's mind does not see it the same way. A strong mind is a mind in control. A baulking athlete is an athlete with an "out of control mind." In order to provide some control to the athlete's mind you can start by assuring and working confidence in the build up skills/drills/and spotted attempts. Providing execution que words, words during the skill, you can provide a structure to the mind. With structure this is one way the mind can feel in control and can communicate efficiently with the rest of the body.
I ask our athletes, "who is driving the bus?" We speak about them having to drive their own bus. On the bus is that anxiety, the fearful, the tentative, assertive, the smart and the confident/courageous athlete. When this needs review, we write down all the different athletes on a white board. We have discussions how to identify who is "driving." Our work then is to get the confident/courageous athlete to drive and banish the others to the back of the bus. The girls, when they are having difficulty will frequently admit that they are struggling to "drive the bus." We then go to drills/other surfaces and spotting to get back into the "driver's seat."
The "driving the bus" metaphor does not really apply to the non-drivers, but all seem to understand putting the different emotions and thoughts in " order."
As I write the above, I know my suggestions to building courage are not achieved quickly. Slow and steady has been my experience. Best, Eric -