Now twisting one face works, but if i twist another face on another axis than, one corner-piece of the edge, that belongs to both twists is not re-parented for twisting this time.
Which one it is, depends on the direction of the first twist.
It seems, that the reason for this are not hidden inaccuracies in the translation values, because it also happens, if i cast the translation value to an int for comparing.
I tested this with this print-command:
print(cubie.name, ": ", offset, " = ", cubie.translation.x, " -> ", cubie.translation.x == offset)
Output for the not re-parented piece:
Cubie1: 1 = 1 -> False
Which one it actually is, depends on the rotations on the first chosen axis.
Here is the repository of my project: