moteurs tronçonnés

11:29 Jan 8, 2017 

Way out of my field, but am wondering if it could be referring to the motor-assist system, going by the detailed description of fly systems on Wikipedia https://en.wikipedia.org/wiki/Fly_system which refers to the small motor size:
"A conventional counterweight system may be automated by the incorporation of a motor and controls, in what is commonly called a motor-assist system. By using counterweight in such a manner, motor sizes can be kept relatively small." "Motor-assist systems very closely resemble standard counterweight fly systems described above, however a drum winch, typically mounted behind the locking rail below the arbor, is used to drive a steel cable purchase line. The purchase line is still terminated at the top and bottom of the arbor, but a rope lock is not used on the motor-assist line set. Weight on the arbor helps balance the batten load so that hoist motor size can remain relatively small."

11:01 Jan 8, 2017 

Is it possible this refers to only a part of the motor mechanism (that which is high in the flies at the 18 meter level). Fly systems are often accessible at various heights, from stage level on up. It wouldn't be surprising that only part of the mechanism was damaged, while that at other levels remains intact.