Quoting from the great commentary by mediaevalfishsandwich:

Khn breaks a string.

The assistant is a general tech, not a guitar tech, he tries to pull the remainder of the string out of the capstan with his Leatherman, not realising that the string is locked/clamped. Khn eventually unlocks the machine head (thumbwheel on rear) 00:24, the tech is then able to remove the string. Tech replaces string, and winds it on as if it is a conventional machine head (multiple wraps). After tech finishes, Khn relocks the machine head 02:04. Throughout the entire process, Khn keeps playing with his RingerBringer on max.

One might infer that they don't have a roadie, and they don't always have a backup guitar (or prefer to change string rather than change guitar?).

Either way, even a string change is entertaining.