Do incarnated angels sometimes crash and burn because of life’s difficulties, and then need karmic repair, as with the Lightworker Healing Protocol?

This, in fact, happens and your client is a case in point. All who come into the earth plane take risks in doing so. This is true of the angelics. They are given special protections and have some strength in numbers they can summon if needed. But they do get in harm’s way at times and this is especially true when they are incarnated as a physical human, because then they lack their normal reach energetically, which normally would be sufficient to keep them safe under any condition. The opposite is true as a physical human. They are sitting ducks like everyone else, other than holding a pretty high vibration for the most part. There are still ways they can be manipulated and fooled into allowing entry of other spirit beings. Keep in mind that as an incarnated human being they become cut off from their past and are disconnected from the divine, largely. Although we serve as the higher self and we can be heard, we must keep it on a fairly subtle level to follow the rules of engagement which now apply to the angelics, that we cannot give them a greatly preferred status but expect them to live under similar rules and constraints as human beings do. They already are a built-in asset because of their lineage and history. They are capable of bringing much light in, and staying in divine alignment during the course of their lives, which will make them much more effective as a person than most humans, who will often falter, become cynical, and may well develop a severely distorted personality with great selfishness if not narcissism. All is a consequence of the harsh life circumstances humans must face routinely. The fact they are groomed to fit within the human makeup is what allows them to be healed in the same way you would heal a human, because it is that humanity that is the liability and where the trauma occurs and continues to reside within their being, when they encounter harsh circumstances and need help because it is more than they can handle.